This example does a lookup when one column is updated and places the result in another column.
Private Sub DataGrid1_AfterColUpdate (ColIndex As Integer)
If ColIndex = 1 Then
Data1.Recordset.FindFirst "PubId = " _
& DataGrid1.Columns(1).Value
If Not Data1.Recordset.NoMatch Then
DataGrid1.Columns(2).Value = _
Data1.Recordset.Fields("Publisher")
Else
DataGrid1.Columns(2).Value = "No Match"
End If
End If
End Sub