Using Two Dates To Figure The Amount Of Days In Between

I have three text boxes. One text box holds a beginning date, a second holds an end date, and the third box holds the number of days in between. I would like the page to figure out the number of days in between the two dates without having to type in the number of days.

Is that possible to do without having to use some kind of confirmation page. I mean using a confirmation page would work also, but I wanted to cut out the number of steps that a user needs to complete the assigned task.

Text Box 1: Beginning Date
Text Box 2: Ending Date
Text Box 3: Number of Days in Between