I want to sum only the values that = certain criteria. For example I have a text field "TypeOfPump" which can be Pump1,Pump2,etc. I also have number field "FlowRate" which can be 20,50,200 etc. I want to sum all of the fields that contain Pump1 only. I can sum with no problem, just when I try to use criteria. Here is my expression that I used for the control source in a text box on the report, it turns the value 0. =IIf(Sum([FlowRate]),([TypeOfPump])="Pump1"). I pretty sure what I want to do is possible. If anyone has any suggestions, it would be greatly appreciated!

You have the sections of the Iff function transposed. It's Iif(expression,truepart,falsepart). In your example it would be =IIf([TypeOfPump]="Pump1",Sum([FlowRate])).

However, assuming these field names are also the name of fields in your table you'd be better served using a DSum function in the AfterUpdate property of your TypeofPump field. Example:

TypeofPump.AfterUpdate
dim strPump as String
strPump = Me!TypeofPump
DSum("[Flowrate]","[YourTableName]","[TypeofPump]= """ & strPump & """")

This will sum the flowrate for any type of pump that is chosen.

Thanks for taking time to answer my question, but I couldn't get it to work. I have my text box in the Report Footer, and my report prompts for criteria driven by a query, thats why I don't think I could use the DSum like you suggested. When I run the report I get no sums at all. Some of the fields are blank so I tried using the IsNull and got a sum, but it was of all pumps, not the one I used in the expression. Here is what I tried. "=IIf(IsNull([TypeoFPump]="Pump1"),"",Sum([FlowRate]))". This seems like it would be easy, but it sure is frustrating me. Thanks again for you time.