I think I understand. You're likely looking for Dynamic NAT, which I've seen on ASA appliances but have never attempted with any other Packet Switching Appliance (e.g. Routers, ISR, etc.).
Do you have an ASA55XX? Is this appliance located in an area where the appliances will pass through?
If so, I can walk you through the ASDM method of pulling this off. It's extremely easy to do, in that the layout of the page is identical to what you're describing you want to do. Under Configuration ==> Firewall ==> NAT Rules, add a new translation (before, after, between in any way that works for your setup). The window that pops up will provide a few criteria. Define the Source interface (if necessary, as it defaults to "Any"), the Destination interface (again, if necessary), the address range for source, the address range for destination (as in, the old server destination), and the service (tcp/4728).
Under the "Action: Translated Packet", do a static NAT, keep source address as "--Original--", and set the destination address to the desired IP address (192.168.98.100). Keep the service the same, or change it if necessary, and make sure the direction is set to a specification you are satisfied with (defaults to "Both", but unidirectional may be desired for security and clarity).
I've had mixed results, but it generally goes off without a hitch.
