convert waistband to elastic

If the skirt is too big you might be able to do it; if the skirt's too small you probably won't.

Check out the info in this old topic. It is the reverse of what you want to do, but the information and links should still be helpful.

http://able2know.org/topic/144041-1

Also, here is another site to browse:

http://www.ehow.com/how_2095663_elastic-waistband-skirt.html