Repeat data from a given date

I am currently updating an old Db which rosters staff. One of the enhancements will allow the user to automatically allocate staff details to a Roster after a given date. i.e. Roster date 20th Feb 15, repeat for 3 days. 21st 22nd 23rd Feb 15. I have created a form with a medium date field and then a Combo box with drop down values of 1 thru 7 days. I want to link the combo box value to the Date box. Any help would be appreciated.:)

Repeat data from a given date