Problem for setting the calendar.

[Jun Ting]

I have the database that will store the information of  "Mon, Tue, Wed, Thurs, Fri, Sat".

I want have a function that when my database (Mon) is not empty, then  user can select one of  the date which is fall in Monday.

For example:
In my database, the "Tue" & "Fri" is not empty. Then the user only can select the date that is on Tueday or Friday. For the date on Monday,Wednesday, Thursday,Saturday and Sunday is set to not selectable.