Terminal Services+Citrix with NAT router

I have a Citrix/TS server behind a NAT router… not a problem in general since I simply use the “ALTADDR” command to allow remote users to connect to it over the single, public IP address of the router. The problem is that the router’s IP is dynamic. Therefore, I need to enter a new ALTADDR command every time I get a new IP address on the router. I need an automated way of running the ALTADDR command with my dynamic public IP “ALTADDR /SET {public IP}”. HELP!