formula question that would use a date range instead of column range?

[lilsnoop]

Hello,

I have a work schedule that uses the following formula in a worksheet titled Payroll:
=SUM(IFERROR(--SUBSTITUTE(UPPER(INDEX(May!$Q$5:$AD$49,MATCH(Payroll!$FL4,May!$A$5:$A$49,0),)),UPPER($A$2:$A$14),""),0))

Would it be possible to edit this section of the formula "(INDEX(May!$Q$5:$AD$49," upon which the formula currently looks for certain criteria between columns "Q" and "AD" on the May worksheet; a formula (one of many) I have to edit yearly to adjust to a new date range. Instead I would prefer the formula to look at two separate cells with dates in them on the Payroll sheet like in cells "FM2" & "FQ2" and then any of the criteria the formula above is trying to match and look for would instead look for the data by looking for the criteria >=FM2 but <=FQ2 from dates listed on the May worksheet range starting from 05/01/15 in cell C1 through 5/31/15 in cell AG1.

I don't have a sample workbook yet that I can add, but I'll try making one if my request is too complicated without one. Thanks to anyone willing to take the time to look at this!

[lilsnoop]

I thought something like this might work but it says it has too many arguments:
=SUM(IFERROR(--SUBSTITUTE(UPPER(INDEX(May!$C$1:$AG$1,">="&$FM$2,May!$C$1:$AG$1,"<="&$FQ$2),MATCH(Payroll!$FL4,May!$A$5:$A$49,0),)),UPPER($A$2:$A$14),""),0))

[lilsnoop]

Anyone have any suggestions? or this just not doable? Thanks!

[lilsnoop]

Any alternative formula suggestions? I've been searching the net, but without success.