Unload duplicateMovieClip

how do i load a movie clip SYMBOL at the highest level and then unload it.

i dont want a SFW or JPG to be loaded- that would be one of the symbols from the same swf file.

the issue is- i have used “getNextHighestDepth()” to create movie clips… now i need to add a box on top of that- so again, i will have to use “getNextHighestDepth()” - which im having hard time to unload (when i use duplicateMovieClip) -

PLEASE HELP- i spent all day yesterday to resolve it.