saving Datagrid edits to the Database

[eljapo4]

Hi - I'm creating an admin application that will allow specific users to manage users login credentials for an application. On a form I have a datagrid that is populated by selecting * from Operator table on the DB. I want the admin users to be able to add, edit and delete records from the datagrid and i have enabled these properties on the grid but any changes need to be confirmed by clicking a 'Saves Changes' button. Here's the code behind this button:

Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
        Const cSUBNAME As String = "btnSave_Click"
 
        Try
 
            'Open the DataBase connection which will be used to execute the SP
            If DatabaseConnectionOpen() = False Then
                Call WriteError(cMODULENAME, cSUBNAME, Err.Number, Err.Description)
                GoTo ExitNow
            End If
 
 
            Dim cb As New SqlCommandBuilder(da)
 
            cb.GetUpdateCommand()
            da.Update(dt)
 
            DatabaseConnectionClose()
 
            FillOperatorGrid()
ExitNow:
        Catch ex As Exception
            Call WriteError(cMODULENAME, cSUBNAME, Err.Number, Err.Description)
        End Try
 
    End Sub

I have added a new record but when I save these changes I am getting this error: "02/12/2011 11:43:56,frmOperator,btnSave_Click,5,Dynamic SQL generation for the UpdateCommand is not supported against a SelectCommand that does not return any key column information."

Can anyone enlighten me as to what is wrong please?