Sound object question

Im making a drum machine/mixer with the ability to choose/change the sounds played through a little “browser”… but i want to be able to code it so that the sounds already in use are greyed out (unselectable).

So is there anyway of getting/reading the linkage identifier name of a sound object?

i.e. if you use:

_root.beat.attachSound("beat");

…the identifier name is “beat”… so in my little beat machines sound browser that one would be unselectable.

any ideas?