Can you mask in Sony Vegas movie studio 9.0 Platnum?

Photoshop

Yes you can. Check mask generator video effect. And the mask composition mode.

But, if you are talking about cutting out frame by frame, no. If you want to do that, you can download a photo editing software like Photoshop or something free like gimp http://gimp.org/ and you can put each frame on that and cut it out frame by frame.

NO you can not mask using Sony Vegas movie studio 9 platinum - you can only use the cookie cutter option.