3D Studio Max 7: Gravity and the Superspray

Hey y'all, I'm in need of help.

Ok, I made a superspray and used metaparticles. But, for some reason, I can't bind my superspray to gravity. The tutorials I read tell me to select the Gravity Binding (WSM) from the modifier list, but it isn't there.

Is there a plugin I'm missing? Is there another way around it?

I can get the PFsource to be effected by gravity, but the only problem is that I can't use metaparticles with it (either that or I just don't know how to if its possible).

Any help would be greatly appreciated. Thx in advance, y'all.