Formula to count weekdays in a range of dates?

I am a fairly new Crystal user (Crystal Reports 11) and not very technical.

I have created a report with parameter prompts to enter a starting and ending date, and want to calculate the number of weekdays within that range (to determine the number of regular work hours within that time frame).

I can calculate the total number of days, and have a parameter for the number of holidays to reduce my day count accordingly, but would like to use a formula to count the number of weekdays. Is this possible?

Thanks!

Lois