Getting object position in screen coordinates

[v-Salik]

I have a user moving an avatar from the 3rd person view (moving arms/hands).
I want to check if the avatars hand is 'on top' of an on object from the view of the user, is there a way to get the projection transformation matrix and apply that to the object positions to get the screen coordinates of both objects then compare them?

THanks
-Salik