AAAaaahhhh Multiple Sheets Multiple Criteria

Please help, I have struggled with this for a week!! And I'm not sure how to explain it.

I have attached a spread sheet with three example sheets on it (in reality these are three seperate sheets)

If there are three mth 1's in the programme multiple units sheet I want it to go to the cashflow single unit sheet and multiply sales in mth 1 by three and then return the sum in cashflow multiple units.

But I want it to be able to do that for mths 2, 3 etc and return the total in the cashflow multiple units.

ie. apr 08 would have 3 lots of sales month 1, plus 3 lots of mth 2 sales
then on the deposits line it would have 3 lots of deposits month 1 plus 3 lots of mth 2 deposits.

I'm not sure if I'm making much sense now because I've gone round in circles so much I'm getting dizzy. I feel that sumproduct may be the answer but have not used it before.

Hopefully the spread sheet will clarify what I'm trying to say (I have attached it but can't see it on the preview?). But any questions for clarification or suggestions would be HUGELY appreciated.