Question

I have an Access form with a textbox that is uses as an expression as it’s controlsource to calculate a value to display. While the below expression works fine in Access 2003, it doesn’t display in Access 2007 automatically. Only when I click on the field, does the value display. What is does is it checks the database for a value based on other fields on the form. If its NULL, the field displays a “N/A”. If it’s not NULL, it displays the value found in the database.

Does anyone know what I might be doing wrong?

=IIf
(
    IsNull( DLookUp("SomeField","SomeTable","SomeField = Forms!frm_FormName!cboSomeCombobox")),
    "N/A",
    LookUp("SomeField","SomeTable","SomeField = Forms!frm_FormName!cboSomeCombobox")
)

Answer 1

Issues that are fixed in Access 2007 by the 2007 Microsoft Office suites Service Pack 1

On a Windows Vista-based computer, fields that are bound to time-intensive 
expressions are blank in Access 2007

Fields that are bound to time-intensive expressions are blank in Access 2007. 
These fields are empty until you click the text box or until you click anything
outside of Access 2007 if the following conditions are true:
The Control Source property of a text box uses the DLookup() function.
The query that is called by the DLookup() function references a control on 
a form.

http://support.microsoft.com/kb/942378