Use Parameter in query

I wrote this code and i can populate result of query to combobox1.but i want to use parameter in my query and i want to range next combobox(such as combobox2) in attention to the selected item in combobox1.My sample databese name is test1 and has 3 field:categoryID,ParentID and Title.Please Help me
here is my code

Dim DataAdapter As OleDbDataAdapter = New OleDbDataAdapter()
Dim myConn As OleDbConnection = New OleDbConnection
Dim sqlStr As String
'Dim conStr As String
Dim dviewmanager As DataViewManager
myConn.ConnectionString = "Provider=microsoft.jet.oledb.4.0;data source = C:\Documents and Settings\sce\Desktop\test1.mdb"
'myConn = New OleDbConnection(constr)
myConn.Open()
'TextBox1.Text = "wsaaAS"
sqlStr = "Select Title From Table1"
DataAdapter = New OleDbDataAdapter(sqlStr, myConn)
'Test1DataSet = New DataSet()
DataAdapter.TableMappings.Add("testmapping", "Table1")
DataAdapter.Fill(Test1DataSet)
dviewmanager = Test1DataSet.DefaultViewManager
ComboBox1.DataSource = dviewmanager
ComboBox1.DisplayMember = "Table1.Title"
myConn.Close()

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thank you very much.
Can you give me the name of the afterupdate equivalent event in vb please.

I have no idea what "afterupdate" event you mean. If you want to know what events the ComboBox class has and what they are for then open the MSDN documentation for the ComboBox, navigate to the event list and read. They're all listed with a description and a link to their own topic, which will often contain a code example.

I wrote a code.but when i select a value from combobox1 i want to show items in combobox2 that are related to the combobox1.Now by my code when i select item in combobox1,combobox2 values are all of the rows in in second field.Please help me what can i do.Please

Imports System
Imports System.Data
Imports System.Data.OleDb
Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'TODO: This line of code loads data into the 'Test1DataSet.Table1' table. You can move, or remove it, as needed.
Me.Table1TableAdapter1.Fill(Me.Test1DataSet.Table1)


End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim DataAdapter As OleDbDataAdapter = New OleDbDataAdapter()
Dim myConn As OleDbConnection = New OleDbConnection
Dim sqlStr As String
'Dim conStr As String
Dim dviewmanager As DataViewManager
myConn.ConnectionString = "Provider=microsoft.jet.oledb.4.0;data source = C:\Documents and Settings\sce\Desktop\test1.mdb"
'myConn = New OleDbConnection(constr)
myConn.Open()
'TextBox1.Text = "wsaaAS"
sqlStr = "Select Title From Table1"
DataAdapter = New OleDbDataAdapter(sqlStr, myConn)
'Test1DataSet = New DataSet()
DataAdapter.TableMappings.Add("testmapping", "Table1")
DataAdapter.Fill(Test1DataSet)
dviewmanager = Test1DataSet.DefaultViewManager
ComboBox1.DataSource = dviewmanager
ComboBox1.DisplayMember = "Table1.Title"
myConn.Close()
End Sub

Private Sub ComboBox1_SelectedValueChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedValueChanged
Dim DataAdapter As OleDbDataAdapter = New OleDbDataAdapter()
Dim myConn As OleDbConnection = New OleDbConnection
'Dim sqlStr As String
'Dim conStr As String
Dim sql As String
Dim dviewmanager2 As DataViewManager
myConn.ConnectionString = "Provider=microsoft.jet.oledb.4.0;data source = C:\Documents and Settings\sce\Desktop\test1.mdb"
'myConn = New OleDbConnection(constr)
myConn.Open()
'sqlStr = "Select Title From Table1"
sql = "SELECT ParentID FROM Table1 WHERE Title = '" & Me.ComboBox1.SelectedText & "'"
DataAdapter = New OleDbDataAdapter(sql, myConn)
'Test1DataSet = New DataSet()
DataAdapter.TableMappings.Add("testmapping", "Table1")
DataAdapter.Fill(Test1DataSet)
dviewmanager2 = Test1DataSet.DefaultViewManager
ComboBox2.ResetText()
ComboBox2.DataSource = dviewmanager2
ComboBox2.DisplayMember = "Table1.ParentID"
myConn.Close()
End Sub
End Class