First you'll have to find out the start date of the current week. Please take a former solution I posted here on CP as a reference on how to do that:
I want to get all the list of week[
^].
It's a piece of cake from there. All you have to do then as add the appropriate number of days to that start date according to your combo list box. You should remember though that different cultures have differen starting days for a week. Please also refer to my former solution for that.
Cheers!
—MRB