txtBox to (datatable) DataGridView

Hello guyz!!!!
I am new at coding and i have a problem....I have tried sooooo many solutions....But NOTHING!!!!
So, I have to forms: main form --> frmKyria , and form2.
In frmKyria there is a DataGridView1 that is datatable(I don't know what exactly does the datatable, but i found that code in order to save the data).
Now, that i want is to add the text from 4 textboxes in form2 to frmKyria DataGridView1 in 4 cells in a row!
p.s. the DataGridView collumns are made programmatically!
Main Form Code(frmKyria)

Code:

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Imports System.Xml
Imports System.IO
Public Class frmKyria
    Private filePath As String = "save.xml" 'xml filepath
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Form3.Visible = True
    End Sub
#Region " User Defined Function "

    Private Function CreateEmptyTable(ByVal TableName As String, ByVal ParamArray ColumnNames() As String) As Boolean
        Dim writer As New XmlTextWriter(filePath, System.Text.Encoding.UTF8)

        Try
            writer.WriteStartDocument(True)
            writer.Formatting = Formatting.Indented
            writer.Indentation = 2
            writer.WriteStartElement("Table")
            writer.WriteStartElement(TableName)
            For Each ColumnName As String In ColumnNames
                writer.WriteStartElement(ColumnName)
                writer.WriteString(String.Empty)
                writer.WriteEndElement()
            Next
            writer.WriteEndElement()
            writer.WriteEndElement()
            writer.WriteEndDocument()
            writer.Close()
        Catch ex As Exception
            MsgBox("Cannot create new table.")
            Return False
        End Try

        Return True
    End Function
    Private Function FormatDgvMstUser(ByRef ObjDgv As DataGridView) As Boolean

        cArith.Name = "clmArith"
        cArith.HeaderText = "Άρ."
        cArith.Width = 49
        cArith.DataPropertyName = "clmArith"
        cArith.Visible = True
        cArith.ReadOnly = False

        cAFM.Name = "clmAFM"
        cAFM.HeaderText = "ΑΦΜ"
        cAFM.Width = 100
        cAFM.DataPropertyName = "clmAFM"
        cAFM.Visible = True
        cAFM.ReadOnly = False

        cOnoma.Name = "clmOnoma"
        cOnoma.HeaderText = "Όνομα Επιχείρησης"
        cOnoma.Width = 180
        cOnoma.DataPropertyName = "clmOnoma"
        cOnoma.Visible = True
        cOnoma.ReadOnly = False

        cPoso.Name = "clmPoso"
        cPoso.HeaderText = "Ποσό"
        cPoso.Width = 80
        cPoso.DataPropertyName = "clmPoso"
        cPoso.Visible = True
        cPoso.ReadOnly = False

        cImerominia.Name = "clmImerominia"
        cImerominia.HeaderText = "Ημερομηνία"
        cImerominia.Width = 190
        cImerominia.DataPropertyName = "clmImerominia"
        cImerominia.Visible = True
        cImerominia.ReadOnly = False

        Try
            ObjDgv.Columns.Clear()
            ObjDgv.Columns.AddRange(New DataGridViewColumn() {cArith, cAFM, cOnoma, cPoso, cImerominia})
        Catch ex As Exception
            MsgBox("Cannot format datagridview.")
            Return False
        End Try

        Return True
    End Function

#End Region
    Private Sub frmMain_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim xmlFile As XmlReader


        'if file doesn't exist, create the file with its default xml table
        If Not File.Exists(filePath) Then
            If Not Me.CreateEmptyTable("Apodeiksi", "clmArith", "clmAFM", "clmOnoma", "clmPoso", "clmImerominia") Then End
        End If

        'fill dataset with selected xml table
        xmlFile = XmlReader.Create(filePath, New XmlReaderSettings())
        ds.ReadXml(xmlFile)
        xmlFile.Close()

        'init datagridview
        Me.DataGridView1.DataSource = ds.Tables(0)
        If Not Me.FormatDgvMstUser(Me.DataGridView1) Then End
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click


        Me.DataGridView1.EndEdit()
        dt = Me.DataGridView1.DataSource

        Try
            dt.WriteXml(filePath)
            MsgBox("Data has been saved.")
        Catch ex As Exception
            MsgBox("Data cannot be saved.")
        End Try
    End Sub
End Class

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Form 2 Code

Code:

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Private Sub btnEisagwgiform2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEisagwgiform2.Click
        'elegxos an to AFM einai 9-psifio kai einai mono arithmoi to POSO kai to AFM
        If IsNumeric(txtAFM.Text) = True Then
            If txtAFM.TextLength = 9 Then
                If IsNumeric(txtPoso.Text) Then
                    synoloPoso = synoloPoso + txtPoso.Text

                    'Metritis gia tin arithmisi twn apodeiksewn
                    metritisApod = metritisApod + 1

                    'Kataxorisi kai dimiourgia stilwn kai kataxwrisi se pinakes gia euresi megaliterou
                    Here i want your HELP!!!!
                    pinakas_afm(metritisApod) = txtAFM.Text
                    pinakas_onoma(metritisApod) = txtOnoma.Text
                    pinakas_poso(metritisApod) = txtPoso.Text

                    'Eyresi sunolikou posou
                    frmKyria.txtbSynoloapodeiksewn.Text = synoloPoso

                    '
                    If (frmKyria.ProgressBar1.Value + txtPoso.Text) > frmKyria.ProgressBar1.Maximum Then
                        frmKyria.ProgressBar1.Value = frmKyria.ProgressBar1.Maximum
                    Else
                        frmKyria.ProgressBar1.Value = (frmKyria.ProgressBar1.Value + txtPoso.Text)
                    End If
                    '
                    '
                    Me.Close()
                Else
                    MsgBox("ΠΑΡΑΚΑΛΩ ΕΙΣΑΓΕΤΕ ΠΟΣΟ", MsgBoxStyle.Information, "***ΠΡΟΣΟΧΗ***")
                End If
            Else
                MsgBox("ΠΑΡΑΚΑΛΩ ΜΟΝΟ 9-ΨΗΦΙΟΥΣ ΑΡΙΘΜΟΥΣ ΣΤΟ ΑΦΜ", MsgBoxStyle.Information, "***ΠΡΟΣΟΧΗ***")
            End If
        Else
            MsgBox("ΠΑΡΑΚΑΛΩ ΜΟΝΟ ΑΡΙΘΜΟΥΣ ΣΤΟ ΑΦΜ ΚΑΙ ΣΤΟ ΠΟΣΟ", MsgBoxStyle.Information, "***ΠΡΟΣΟΧΗ***")
        End If
    End Sub

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If you know another way to save,load,update the datagridview to xml just tell me the way i will code....
maybe the code in main form(up) is problematicly and doesn't allow me to add a new row