Adding a NULL route to DNAT

Hi all
As a temp measure at a customers site I want to add a NULL address ie 0.0.0.0 or 127.0.0.1
to a dnat rule until I can get the customer to supply me with IP address of incoming address's for a Terminal Server somebody else has used any with auto rules.

Why can I not add a Host 0.0.0.0 or 127.0.0.1

Thanks

Mark