Yes, ... By CEX i imagine you have Hybrid Firmware to perform the mods.. You can install a simple HFW 4.84 & 4.85 now, directly on any console.
Anyway, the method is to either get a modified Eboot, or Mod your own using an Eboot builder, i believe MW2 & MW3 have Eboot builder's.
You can also edit your Eboot to include a plugin ( SPRX Etc ) ..
You need to specifically look up the game and then a mod menu for that specific CFW / HFW ..
So, "MW2 SPRX HEN"
On another note, RTM Tools are also compatible by using WebMan "PS3Manager api - in WebMan Setup" & "Fake CCAPI" ..
It is a little annoying to replace the PS3lib in each tool, but once replaced you can use nearly any RTM Tool on your PC ...