Dynamic Linkmasterfields

[Liveson]

Hie

I have an unbound form on which there are 3 controls: option group, combo box and a subform. The value of the combo box depends on the value of the option group and the value of link child field depends on the value of the combo box. here is the code:

Dim stSQL As String, stCriteria As String, stDocNo As String
 
stDocNo = Me.cboDocNo
 
If Frame4.Value = 1 Then
    stSQL = "SELECT [DeliveryNotes].[DeliveryNote], [DeliveryNotes].[Consignee], [DeliveryNotes].[Description], "
    stSQL = stSQL & "[DeliveryNotes].[ClientID] FROM [DeliveryNotes]"
Else
    stSQL = "SELECT [ExpiryDates].[ItemTransID], [ExpiryDates].[InvoiceNo], [ExpiryDates].[Description] "
    stSQL = stSQL & "FROM [ExpiryDates]"
End If
 
Me.cboDocNo.RowSource = stSQL
Me.DeliveryTrans.LinkMasterFields = stDocNo
If Frame4.Value = 1 Then
    Me.DeliveryTrans.LinkChildFields = "[DeliveryNoteNo]"
Else
    Me.DeliveryTrans.LinkChildFields = "[InvoiceNo]"
End If
 
Me.cboDocNo.Requery

This code is set to run when the option group is updated but I'm getting a runtime error. I'm actually prompted for a parameter value. If the value of the combop box (stDocNo) is, for example, 5 I'm prompted for a parameter value of 5. If I haven't entered anything yet I get "Invalid use of null" error. Is there something I'm missing? Please help.

Regards

Liveson

[joannem]

would a discrepancy in name be an issue

Me.DeliveryTrans.LinkChildFields = "[DeliveryNoteNo]"


stSQL = "SELECT [DeliveryNotes].[DeliveryNote],


jo