How to interrupt preloading of external swfs?

Problem:
I am loading a number of external swf files into one “master” swf. The user can press buttons to trigger the preloading of an external swf. Loading is working fine, except that rapidly pressing a button or pressing multiple buttons will start a huge list of preloads.

What I want:
I want only one swf to be preloaded at a time. The project should allow a user to “switch” to loading a different swf while one is already in the process of preloading.

What I have:
I have external swfs preloading properly using the typical Loader class methods. I have seen script like loader.close() and unloadAndStop(), but I can’t figure out how they apply.

Any direction to a sample, or code would be appreciated.