Sumproduct with different sized column arrays

[adambriggs]

Hi all,

In the spreadsheet attached, I would like to convert annualised costs into a monthly forecast by category. The complication is that there is a timing section by month (i..e percentage of cost in that month) which needs to be taken into considertation. So formula should multiple the year value by the percentage for the month, then sum all those for a given category. Would like to also add condition of greater than start month (timing) and less than max year (end date) but probably simpler once the above is solved for.

Many thanks in advance for any help.