Is there an alternative to SUMPRODUCT multiple sheets on a closed work book

Hi

I have the following formula which works on 1 sheet (MAY) however I want it to work on all 12 sheets across the work book,

Example

='[File Allocation 2015 - 2016.xlsx]APR:MAR'!$C$3:$C$2500

3d cell references wont work because its a sumproduct

I don't want to change to another function because its referencing a closed work book

Is there anyway to get this to work the way I want it?


=SUMPRODUCT(SIGN(('[File Allocation 2015 - 2016.xlsx]MAY'!$C$3:$C$2500>=$D$5)*('[File Allocation 2015 - 2016.xlsx]MAY'!$C$3:$C$2500<=$E$5)),--('[File Allocation 2015 - 2016.xlsx]MAY'!$A$3:$A$2500='Hidden Calculations Sheet'!$K3),--('[File Allocation 2015 - 2016.xlsx]MAY'!$I$3:$I$2500<>"R"))

me too unfortunately they want the source book to be separated by month on different tabs,
perhaps i can maybe find a way to use the consolidate feature on the source book onto a hidden sheet

i guess i will have to do a sumproduct for each tab and add them together, and see if that will work.

i will have to play around and think about it i guess