how to fill data to combobox from selected value from first combobox value

Private Sub cmb1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmb1.SelectedIndexChanged,cmb1.SelectedValueChanged
Try
if IsNumber(cmb1.selectedValue) Then
              Sql = "SELECT * from stock where brand=" & cmb1.SelectedValue

              ds = objStock.ShowAllRequiredInStocks(Sql)

              cmb2.DataSource = ds.Tables(0)
              cmb2.displaymember="Item"
              cmb2.valuemember="ID"
End If
Catch
End Try
    End Sub

Private Sub cmb2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmb2.SelectedIndexChanged,cmb2.SelectedValueChanged
Try
If IsNumber(cmb2.SelectedValue) then
              Sql = "SELECT * from stock where item=" & cmb2.SelectedValue

              ds = objStock.ShowAllRequiredInStocks(Sql)

              cmb3.DataSource = ds.Tables(0)
              cmb3.displaymember="Price"
              cmb3.valuemember="ID"
End If
Catch
End Try
    End Sub