Running Sum with Calculated Control

[Kelley]

I am using XP and have an calculated control with an IIF function in it. I have Running Sum Over Group in the properties, but the sum will not run. It worked okay in Access 97, but won't work with this version. Ideas?

 

[Nouba]

What does the ControlSource say?

 

[Kelley]

The control source says: =IIF([OptionDate]<Now(),[ActualLots]," ")