The following formula was provided to me a while ago so that i could make the
following statement happen for a monthly cash flow...take the month i input
into a cell and then find the corresponding month in another row and then
return the sum of the next 12 months of cash flow. for example, if i entered
12 into the cell, the formula would then go to the cash flow page and find
the corresponding month and then sum cash flows for months 13-24 (the next 12
months). The formula works great, but I have never seen the -- function and
would like to know what it does...thanks!

=SUMPRODUCT(--('Rental Income
Asumptions'!D15:EE15=Summary!E57+1),--('Rental Income
Asumptions'!D15:EE15<=Summary!E57+12),'Rental Income Asumptions'!D16:EE16)