Is it possible to create an equation to provide the number of weeks between 2 dates?

[Web Design UK]

Hi,

I have manage to add a custom field variable that gives me a project DUE end date based on a start date I input manually.

What  would like to be able to do is have a field tht shows the total number of weeks passed between that end date and a field with the project ACTUAL end date manually input.

Is this possible?

Thank you :-)