Model invisible in certain animations?

Im currently working on a doodad request for falling leaves.... what i want to do is make like 8 seperate leaves. Some falling in say Stand animation, some falling in Stand 2 animation , etc. What im not sure about is how to make certain leaves not show in certain animations. Say if i only wanted the brown ones to fall in stand, and the red ones to fall in stand 2? I know this is simmilar to the corpse in all models, where it doesnt show up untill the decay animation, however im not sure how to do this. Can anyone give me some pointers??

you could place them under the ground like the decay animation. but thats the only way i know of.

you use which proggy? Using max is easy-> just add a visibility track as on/off in notetrack for selected object/bone
then apply keys to say when to hide and reveal

I use gmax

also im not sure how to do all those steps... could you explain them to me? Ive never had to use the key thing , not sure what it does exactly. Hopefully it works for gmax too, its supposed to be pretty close to 3ds max , which i cant afford, 4000 dollars, and i cant get used, never seen a used copy of it on any auction sites....cant bootleg it either, never seen any where lol.

*chough* imesh *chough* excuse me.

A) find the bootleg copy one way or another, I doubt Dex extracts it correctly regarding visibility
B) if that fails , you have to manually add the visibility tags in mdl after you exported with Dex (use search button, it has bee discussed plenty of times)