sql conditional statements

[trixxnixon]

i have to introduce a new field now, but i need it to calculate based on a condition being true. the new field is Sumofdays.
the calculation should not calculate if sumofdays
here is my logic. but i know this syntax is way off.

if isnull(sumofdays)=true then
DIH =Workingdays2(DateValue([Date Submitted]),[Date Completed])  
else
Workingdays2(DateValue([Date Submitted]),[Date Completed])- ([Sumofdays})
end if

when i try to use an iif statement, even a simple one i get a
here is what im using in the query design view

NDIH: IIf(IsNull([sumofdays]),Workingdays2(DateValue([Date Submitted]),[Date Completed]),Workingdays2(DateValue([Date Submitted]),[Date Completed])-[(sumofdays])

but i keep getting the paramater input request. what might i be doing wrong?

Thanks!

 

[Brianwarnock]

I suspect sumof days is an alias ie Sum(days) as sumof days, Aliases cannot be used in criteria
isnull(sum(days) has to be used

Brian