You have the parenthesis in the code box different than the calculation you typed in. Look close for the RED parenthesis
Code:
=(Nz([Payment],0)+Nz([Balance],0))*0.01
Here you are adding [payment] and [balance], then multiplying the total by 0.01
Code:
=IIf([ Code ]="SAVE",Nz([Payment],0)+Nz([Balance],0)*0.01,0)
Here you are multiplying [balance] by 0.01, THEN adding [payment] ....NO grouping parenthesis
Try:
Code:
=IIf([ Code ]="SAVE",(Nz([Payment],0)+Nz([Balance],0))*0.01,0)
This has the grouping parenthesis (in RED)
Note: I had to add spaces around the word code because "code" is a tag in the HTML of the page. So ignore the extra spaces around code.