How to remove duplicate movie

im using flash MX 2004.. on my flash screen ive button that can generate item via entering the number u want… for example i want to generate a 10 of dress… so i use loops and duplicateMovieClip()… the problem here is … when i click the back button to go previous page… that 10 of dress which already been duplicate still appear in my previous screen. so … how to remove this???