tcl command for nodes on a surface?

Hi all,

I have a component which consists solid geometry.

I have meshed it by creating a tcl script (only a couple of commands needed for this).

Now I have to apply constraints and loads on some surfaces of this solid (which is now meshed).

I am searching for a tcl command which can give me all the nodes on the surfaces of this meshed component.

I know the commands which are used to get nodes from a component, but there exists no such information about how to get the same from surfaces!

Kindly advise some hints/methods for this purpose.

Best regards,

Mubeen.