Hmmm. Still not working. I tried it in the AfterUpdate of the CertNum textbox and the LostFocus. I have two tables. My Customer table and my Payments table. I did:
Private Sub CertNum_LostFocus()
Me.txtbox_GetBusName = DLookup("BusName", tbl_MainCust, "[CertNum] = '" & Me.CertNum & "'")...