Date Formula

Hello,

I'm doing a weekly forecast model and need some help coming up with the best formula.
If my business has revenue in let's say January, and it takes 2 months to collect, what formula can I use to find 2 months later and spread it by the number of weeks in March?

Second formula, if I pay commission on the 25th of the following month, but sometimes the week does not end on the 25th....what formula can I use to find closest to?

Third formula, is to forecast payment of subcontractors. If I have expenses in a given month, I need a formula that recognizes the month of the expenses and spreads the expenses by the number of weeks in the current month.

Thanks so much....I appreciate the help!

Date2 - Date1 = number of days between the dates. e.g., 10/18/2015 - 8/2/2015 = 77, so those two dates are 77 days apart. Divide by 7 and you get 11, the number of weeks that have passed.