When I tried
IIF(Nz([EST TYPE O],0) >0 And Nz([OPEN CASES],0)> 0,[EST TYPE O] / [OPEN CASES],0)
I got error:Syntax Error (comma)in query expression 'First((Nz([EST TYPE O],0) >0 And Nz([OPEN CASES],0)> 0,[EST TYPE O] / [OPEN CASES],0)
When I tried
Nz([EST TYPE O],1) / Nz([OPEN CASES],1)
I...