Well this can be done pretty easily.. first use material skins, not entity skins. Then simply make a material event like so:

bmap skin1=<skin1.tga>;
bmap skin2=<skin2.tga>;
etc...
function material_event()
{
mtl.enable_render=on;

if my.SKINTPYE=1
{
mtl.Skin1=skin1;
}

etc...

}