"Invalid use of null" when opening a form in Access 2007

[BojanglesWA]

I have a form that displays a list of orders. The form has worked fine until
recently when it gave out the "Invalid use of null" error on opening. The
form triggers no events when it opens. I have created a blank database and
imported the tables, forms etc from the original to the blank hoping that the
problem may have been a glitch but that never fixed it. Can anyone help?

 

[SteveM]

Do you have any fields with DLookup() or another domain aggregate function in
the record source?

If there are no events initiated by the form, it is probably a field looking
up a value or the form's filter setting.

Steve

 

[BojanglesWA]

Do you have any fields with DLookup() or another domain aggregate function in
the record source?

If there are no events initiated by the form, it is probably a field looking
up a value or the form's filter setting.

Steve

Steve

I cant thank you enough. I had an aggregate function calling on a null
field. I am fairly new to databases and this (obviously) was the first time
I had run into this sort of a problem. Thanks again

Brian

 

[SteveM]

Glad to help.

Incidentally, to protect against this error in future you can wrap your
domain aggregate function with the Nz() function (if available in your
version).

For a text field: Nz(DLookup("myField","myTable","myCriteria"),"")
For a numeric field: Nz(DLookup("myField","myTable","myCriteria"),0)

If a Null is encounterd, the first will return "" (zero length string) the
second will return '0'.

Steve