Calc days in month when full and variable month for a budget report

[JOHNAK27]

Hi all

I need to calculate a client's budget monthly over a set period of time. The report may be run for a set of months or single month.

The calculation will need to consider when full month days and when variable, that is, first month and last month of client's budget.
I have attached sample, with partial formula, any assistance in completing would be appreciated.



Many thanks
John