Sumproduct between dates

Hi

I am creating an asset purchase/capitalization plan and in the interest of space and calculation count I have chosen to do a summary monthly depreciation row. I have the first half of the concept down, but how do i get it to Stop after the designated time period (useful life) - Say 3 years (and asset purchased in May 2012 will be done Depr. in May 2015 if it is a three year asset)

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Thanks

Hi
Can not understand please fill some examples to illustrate

However if you want to add a seconf condition use this version

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Regards