Sales in each period between start and end dates

I have a start and an end date of a project and a daily charge and pay rate (the difference being my profit). I want to plot for each calendar month how much profit I will make, using a formula that takes into account working days and knows from the start and end dates which months it needs to put ach value in. If that makes sense.

Attached template for layout and I am looking for the formula in each month to calculate

I hope someone can help, Pat