setting control source from possible null field

[priapus]

I have a text box on a form whose control is the sum of two other text boxes on the form. When both source fields contain data, works fine. One of the source fields, however, is based on a Dsum statement that sometimes results in data but usually results in nothing. What's the easiest way to do this?

 

[BoydW]

I would use an IIF function to test for the contents of the text boxes. If both are blank, then return "", if one is blank, only DSUM the other one, if neither one is blank, DSUM both.

 

[AArt]

You naughty person you.
Try this:
If IsNull(sourcefield) then
'Handle it one way
Else
'Handle it the other way
End if

That should do it

 

[priapus]

haha Art, I think you're the first person to figure that out. Since you can't enter the code builder for the control source of a field (that woulda made it easy) I used the IIF function in the expression builder. Thanks for the help.