Port forwarding with different internal/external ports on Linksys wireless G router

I have a Linksys WRT54G router that I want to set up like I had my old Belkin one setup: I have RDP turned on and exposed via port forwarding, but as port 10000 instead of port 3389. Belkin allowed an external port to be specified for teh internal one, butthe PF option on the Linksys config does not appear to allow specifying a different external port. Is this possible? Right now, I am doing the mapping via my XP firewall (creating a new "port" whose extenral port is 10000 and whose internal port is 3389), but I'd like to do it all from within the router itself if possible.