I seem to be having a lot of problems with the DLookup function. PartNo is PK and is text in table tblPartNo. I am trying to compare this with a field on frmCustomers. The field on frmCustomers is not the PK and is called SlideNo. If the text in the field SlideNo matches the field PartNo, then I want to update a field txtDorM. I can get a text box to display the answer to a straightforward DLookup but not to update a text box. Any help appreciated.