Private Sub YourGrid_CellValueChanged(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles YourGrid.CellValueChanged
If (e.ColumnIndex = -1 Or e.RowIndex = -1) Then
Exit Sub
End If
If (TypeOf YourGrid.Item(e.ColumnIndex, e.RowIndex) Is DataGridViewComboBoxCell And YourGrid.Columns(e.ColumnIndex).Name.ToLower().Equals("YourColumn1")) Then
Dim combotwo as DataGridViewComboBoxCell = DirectCast(YourGrid.Item("YourColumn2", e.RowIndex), DataGridViewComboBoxCell)
combotwo.Items.Clear()
'fill the data here
End If
End Sub