Dbox2 on home Wlan with shared IP.

[Macflame]

I have my dbox and home pc's on a wireless network. The dbox is connected to the Nat Wireless Access Point by cable and the macs and pcs by wireless. The WAP in turn is connected to my DSL modem by cable.
In order to access the internet, cable broadband, the computers share the same IP via the DSL modem, although within the WAP they are assigned their own IP address. Except for the Dbox which has it's own IP.
If I want to transfer files to and from the Dbox I have to assign a PC with an address similar to the Dbox (I've forgotten the tech term!). i.e. Dbox 192.168.1.2
PC 192.168.1.1. All is then well. When I have finished transfers I then change the IP address, on the PC, to be allocated by the WAPs DHP.
I have tried setting up a workgroup containing the Dbox and 1 PC but failed miserably.
Is there a way where I can set up a workgroup within the wireless network so that I didn't have to keep altering IP addresses?