I want the user to put into a cell: Today's date, ie. 10/1/08

Already in another cell will be the Effective Change Date, ie. 6/1/08

The difference there is 4 months.

Here is the formula I need: ((Orignial Price-New Price) * 4 months)

How do I get the 4 months to calculate based on the user inputting todays'
date or on a date of their choice?

Thanks for your help!!