Help w formula for waterfall based on date and multiple criteria

[Musa15]

I am looking for a formula that evaluates start month for Project 1, determines it starts in November, determines number of months to complete and calculates number of transactions per month based off of those cells.

Any help is much appreciated

 

[Musa15]

I think I need to use some combination of sum ifs and index match

 

[DanteAmor]

It would help if you put several examples of what you have and what you expect from the result.
You can copy your range of cells and paste here.