halu...im 3 months aspirant in vb.net i have problem about DataGrid..

i encountered error such as this:
Dynamic SQL generation for the UpdateCommand is not supported against a SelectCommand that does not return any key column information.

and here my sample code:

Private ds as DataSet
dim da as SqlDataAdapter
dim cmdtext as string

//form load
ds = new DataSet("customertable")
cmdtext="select * from customertable"
Dim da As New SqlDataAdapter()
da.SelectCommand = New SqlCommand(cmdText, cn)
da.Fill(ds)
DataGrid1.DataSource = ds
//

Private Sub water_reservation_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing

If ds.HasChanges Then
Dim cb As SqlCommandBuilder
Dim cmd As String = cmdText
da = New SqlDataAdapter(cmd, cn)
cb = New SqlCommandBuilder(da)
Debug.WriteLine(cb.GetInsertCommand.CommandText)
Debug.WriteLine(cb.GetUpdateCommand.CommandText)
Debug.WriteLine(cb.GetDeleteCommand.CommandText)
da.Update(ds)
End If
End Sub

tanx...in advance..