Count clicks in listbox

[zozzie]

I'm trying to detect if a user has clicked an item in a listbox. The reason for this is that if a user has clicked the listbox, then the datasettable that fills the second listbox must be cleared and filled up by another dataadapter.

I've written some code but is doesnt do the job:

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
If blnLoadListbox1 = True Then

Dim strSQLGroup As String

If Me.ListBox1.SelectedIndex > -1 Then
Me.dataset.Tables("tblGroup").Clear()
End If

Try
strSQLGroup = "SELECT GroupDescription FROM tblGroup where tblGroup.MainGroupID=" & Me.ListBox1.SelectedValue.ToString
Dim DAGroup As OleDbDataAdapter = New OleDbDataAdapter(strSQLGroup, connection)
DAGroup.Fill(dataset, "tblGroup")
Catch ex As Exception
MsgBox(ex.ToString)
End Try

Me.ListBox2.DataSource = dataset.Tables("tblGroup")
Me.ListBox2.DisplayMember = "GroupDescription"

End If

End Sub


The code crashes and I get an error message at the line : Me.dataset.Tables("tblGroup").Clear(). The message is the following:

An unhandled exception of type 'System.NullReferenceException' occurred in TypedDatasets.exe

Additional information: Object reference not set to an instance of an object.


Any ideas???

Thanks

Tom