I don't believe you can (although anyone is free to correct me if I'm wrong). You can copy the armature and paste it into a new layer in a frame immediately after the previous layer you copied from, but if you need it to loop multiple times, that solution will require an absurd amount of layers.
Your best best is probably converting the armature into a symbol. By itself, it will loop infinitely without any coding. If you need it to loop a certain amount of times or in response to user input, then you'll need to add the appropriate actionscript.
I have a Flash Extension called Quesy Tools that has
a bunch of handy functions. One of them is a duplicate layer command.
Tonight I tried it on an Armature layer and it worked.
Don't have the URL, you'll have to look it up.