Date Calculation excluding weekends and holiday list

Question

Hi every one,
I m new to program side, I want to create one simple date operation in asp.net
the procedure is simple,

Step1: User want to select course start day in calender control
Step2:Then want to enter duration of the course(in days, like 20 days) in textbox.
Step3:After selection user wants to click the button to calculate the course end date excluding weekend days and holiday list.
step4:Result should show the enddate of course in label or textbox.

Can any one provide the logic for that, i m new for asp.net.

Thank you
Praveen