You could restrict the available bandwidth in the advanced wireless setup for the router (it is buried under advanced security settings for wireless) to a fixed rate that ranges from 1 to 54mbps. The problem is that would be the limit even if the desktop wasn't in use.
However I doubt you really need to do anything unless your laptop and router supports 802.11n. There are very few Verizon supplied routers out there that support 802.11n. So if you are using the Verizon supplied router, 802.11g is probably as fast as it gets. IN theory 802.11g can reach 54mbps, real world tends to be a lot lower.
Absent 802.11n support . It is pretty hard to get 802.11g (and impossible for 802.11b) to be much beyond about 10mbps bandwidth. 802.11n will support considerably higher data rates.
In my experience the the wireless hardware adapter on a laptop with 802.11g is rarely configured with enough buffering to reach 54mbps, even if there were no other impediments. Usually there are plenty of other things to limit the wireless performance.
So the short answer is what you want is likely to happen anyway.
