Uhh, hate to break this to you simon but you could ALWAYS control all device codes 1-16 with your pronto and IR543 using Ivan Luk's quick_x10.ccf file. The IR 543 controls all 16 device but only has hard buttons for 8 of them.

These new codes issue the device command and the on or off in one command so that you don't have to hit device #3 THEN ON, or create a macro to do so.