Calculation of Days in Month

[Brenkenathan]

Is there any way that excel automatically calculates the amount of days in a month?
Here is my problem

I have a spreadsheet to deteremine amount of money to pay for rent.

I have the following columns and I am trying to take out the days in the month colum

-I have a date signed colum
-a Plus 45 days colum because Rent doesnt start to 45 days later(=date signed+46)
-A Current Rent Amount Colum
-Days in month colum
-Per Diem Rate Colum (is Current Rent/days in month)
-Pro Rated Days (If signed date is 9/20/02, calculates days till end of month)
-Rent Due
I want this sheet to be made as simple as I can(for other people are going to be using it) and I dindt know if there is a way to make excel calculate those days for the Per Diem so we arent forced to...
Thanks

 

[Brenkenathan]

As far as I know this looks to have worked...Thank you very much for your time and effort into this.