Progressive calculation based on date and months Update required

RE the attached worksheet.

The formula is in (in Column M – adjusted hours) to calculate progressive payments based on the current day/month/year entered at $O$2 Vs the start month (Column D) Vs the end month (Column E) but it won’t calculate based on a last year start date (2011) and a current year end (2012).

The formula is

=IF(OR(G2<>"ST",$O$2<D2),"",MIN(L2,L2/(MONTH(E2)-MONTH(D2)+1)*(MONTH($O$2)-MONTH(D2)=1)))

I require the formula to calculate a pro-rata payment based on the date entered at $O$2 using the month and year start (Column D) against the end date month and year (Column E).

There also seems to be a problem when it is the same month/year calculation, see row 3 outcome. When you place a February date at O2, it calculates zero, but when you place a March date, it calculates the full 80 hours. It should calculate 80 hours with a February Date. So the formula seems to be a “1” month calculation behind.

The original post is located here: TITLED - Progressive calculation based on date and months

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Hoping you can help,
regards Chris