Updating datagrid from database

Maybe someone can help me with something that I have never been able to grasp, updating the datbase after changing data in a datagrid. I have the code below to load the datagrid and basically it takes a month of data and populates the datagrid. There are 2 combos above the data grid that the use has to select a month and a year and then it will populate. One combo is the month, the second the year. There are also 2 buttons, one for next month, the other for previous. I can go thru the data and it works flawlessly. I am now at the point where I need to figure out how to update the data if the user changes it. I am guessing I would use the dgCharges_CurrentCellChanged sub but not totally sure. Any help would be great. Heres the code.
VB Code:
Dim sqlConn As SqlClient.SqlConnection
    Dim sqlCmd As New SqlClient.SqlCommand
    Dim sqlRead As SqlClient.SqlDataReader
    Dim varNum As Integer = 0
    Dim varTotalMon As Decimal = 0
    Dim varUsage As Decimal = 0
 
    Private Sub LoadGrid()
 
        If cboMonth.Text = "Choose Month" Then
        Else
            If cboYear.Text = "Choose Year" Then
            Else
                If varNum = 0 Then
                    varTotalMon = 0
                    varUsage = 0
                    Dim daPubs As SqlDataAdapter
                    Dim dsPubs As DataSet
                    SqlConnection1.ConnectionString = "workstation id=""S-KG-CFSCE-2098"";packet size=4096;integrated security=SSPI;data s" & _
                                "ource=""SCE-SCE-DSVR02D"";persist security info=False;initial catalog=Telecomm"
                    SqlConnection1.Open()
                    sqlCmd.Connection = SqlConnection1
                    sqlCmd.CommandType = CommandType.StoredProcedure
                    sqlCmd.CommandText = "SPCharges"
 
                    sqlCmd.Parameters.Add("@month", SqlDbType.VarChar)
                    sqlCmd.Parameters("@month").Value = cboMonth.Text
                    sqlCmd.Parameters.Add("@year", SqlDbType.VarChar)
                    sqlCmd.Parameters("@year").Value = cboYear.Text
 
                    daPubs = New SqlDataAdapter
                    daPubs.SelectCommand = sqlCmd
                    dsPubs = New DataSet
                    daPubs.Fill(dsPubs)
                    dgCharges.DataSource = dsPubs
                    dgCharges.DataMember = "Table"
 
                    SqlConnection1.Close()
 
                    SqlConnection1.ConnectionString = "workstation id=""S-KG-CFSCE-2098"";packet size=4096;integrated security=SSPI;data s" & _
                                "ource=""SCE-SCE-DSVR02D"";persist security info=False;initial catalog=Telecomm"
                    SqlConnection1.Open()
                    Dim cmdtext As String = "Select * from Charges where Month like '" & cboMonth.Text & "' and Year like '" & cboYear.Text & "'"
                    da.SelectCommand = New SqlCommand(cmdtext, SqlConnection1)
                    Dim dr As SqlDataReader = da.SelectCommand.ExecuteReader
                    While dr.Read
                        If dr.IsDBNull(2) Then
                        Else
                            varTotalMon = varTotalMon + CDec(dr.GetValue(2))
                        End If
                        If dr.IsDBNull(3) Then
                        Else
                            varUsage = varUsage + CDec(dr.GetValue(3))
                        End If
                    End While
                    txtMonthlyTot.Text = "$ " & CStr(varTotalMon)
                    txtUsage.Text = "$ " & CStr(varUsage)
                    dr.Close()
                    SqlConnection1.Close()
 
 
                    varNum = 1
 
                Else
 
                    varTotalMon = 0
                    varUsage = 0
                    Dim daPubs As SqlDataAdapter
                    Dim dsPubs As DataSet
                    SqlConnection1.ConnectionString = "workstation id=""S-KG-CFSCE-2098"";packet size=4096;integrated security=SSPI;data s" & _
                                                   "ource=""SCE-SCE-DSVR02D"";persist security info=False;initial catalog=Telecomm"
                    SqlConnection1.Open()
                    sqlCmd.Connection = SqlConnection1
                    sqlCmd.CommandType = CommandType.StoredProcedure
                    sqlCmd.CommandText = "SPCharges"
 
                    'sqlCmd.Parameters.Add("@month", SqlDbType.VarChar)
                    sqlCmd.Parameters("@month").Value = cboMonth.Text
                    'sqlCmd.Parameters.Add("@year", SqlDbType.VarChar)
                    sqlCmd.Parameters("@year").Value = cboYear.Text
 
                    daPubs = New SqlDataAdapter
                    daPubs.SelectCommand = sqlCmd
                    dsPubs = New DataSet
                    daPubs.Fill(dsPubs)
                    dgCharges.DataSource = dsPubs
                    dgCharges.DataMember = "Table"
                    SqlConnection1.Close()
                    SqlConnection1.ConnectionString = "workstation id=""S-KG-CFSCE-2098"";packet size=4096;integrated security=SSPI;data s" & _
                                                    "ource=""SCE-SCE-DSVR02D"";persist security info=False;initial catalog=Telecomm"
                    SqlConnection1.Open()
                    Dim cmdtext As String = "Select * from Charges where Month like '" & cboMonth.Text & "' and Year like '" & cboYear.Text & "'"
                    da.SelectCommand = New SqlCommand(cmdtext, SqlConnection1)
                    Dim dr As SqlDataReader = da.SelectCommand.ExecuteReader
                    While dr.Read
                        If dr.IsDBNull(2) Then
                        Else
                            varTotalMon = varTotalMon + CDec(dr.GetValue(2))
                        End If
                        If dr.IsDBNull(3) Then
                        Else
                            varUsage = varUsage + CDec(dr.GetValue(3))
                        End If
                    End While
                    txtMonthlyTot.Text = "$ " & CStr(varTotalMon)
                    txtUsage.Text = "$ " & CStr(varUsage)
                    dr.Close()
                    SqlConnection1.Close()
 
                End If
 
 
            End If
        End If
    End Sub
 
    Private Sub cboYear_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboYear.SelectedIndexChanged, cboMonth.SelectedIndexChanged
        LoadGrid()
 
 
    End Sub
 
 
    Private Sub btnPrev_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPrev.Click
        If cboMonth.Text = "Choose Month" Or cboYear.Text = "Choose Year" Then
            MsgBox("Month and Year must be chosen first", MsgBoxStyle.OKOnly, "Choose month and year first")
        Else
 
            If cboMonth.SelectedIndex = 0 Then
                cboMonth.SelectedIndex = 11
                If cboYear.SelectedIndex = 0 Then
                    cboMonth.SelectedIndex = 0
                    MsgBox("No records before 2006", MsgBoxStyle.OKOnly, "No Records")
                Else
                    cboYear.SelectedIndex = cboYear.SelectedIndex - 1
                End If
            Else
                cboMonth.SelectedIndex = cboMonth.SelectedIndex - 1
            End If
        End If
 
    End Sub
 
    Private Sub btnNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNext.Click
        If cboMonth.Text = "Choose Month" Or cboYear.Text = "Choose Year" Then
            MsgBox("Month and Year must be chosen first", MsgBoxStyle.OKOnly, "Choose month and year first")
        Else
 
            If cboMonth.SelectedIndex = 11 Then
                cboMonth.SelectedIndex = 0
                If cboYear.SelectedIndex = 14 Then
                    cboMonth.SelectedIndex = 11
                    MsgBox("No records after 2020", MsgBoxStyle.OKOnly, "No Records")
                Else
                    cboYear.SelectedIndex = cboYear.SelectedIndex + 1
                End If
            Else
                cboMonth.SelectedIndex = cboMonth.SelectedIndex + 1
            End If
        End If
    End Sub