another nested if quandry

[cookie5]

I had the following sql working correctly:

Sum(([workorders empdetails]![Emp 1 Hours:]*[Employees]![PayRatew/Benefits])/IIf([SBL],2,1)) AS [Totalreg Labor],

Then I had to add another condition checking for checkboxes RTA, RTB, RTC, RTD, RTE. If one is checked I want to multiply by the percentage in RTAper or RTBper or RTCper or RTDper or RTEper according to which check box is checked, so now my sql is

Sum(([workorders empdetails]![Emp 1 Hours:]*[Employees]![PayRatew/Benefits])*IIf([RTA],RTAper,1)*IIf([RTB],
[RTBper],1)*IIf([RTC],[RTCper],1)*IIf([RTD],[RTDper],1)*IIf([RTE],[RTEper],
1)/IIf([SBL],2,1)) AS [Totalreg Labor],

When I run the query with one of the checkboxes checked, it does not multiply by the per for that checkbox.
Any help would be greatly appreciated.....again.

 

[cookie5]

P.S.
RTAper,RTBper,RTCper,RTDper and RTEper are the results from previous queries. When I run the query with the above sql it shows the percentages EXCEPT when the checkbox for the corresponding per is checked, then it does not show the per and puts nothing in the Totalreg Labor field. I hope this better explains my problem.