How can I get a dial string to work

Here is my issue. I am running the pbx in Argentina and we need to be able to dial local numbers, I.E. XXXX-XXXX. The problem is my provider requires me to dial the entire number as if we are calling from the US I.E. 011-54-11-XXXX-XXXX. Now there are several different area codes here and our local would be 11 so I would need the PBX to dial the 011-54-11 and we would just have to dial the 8 digit number just like the regular phone company has it setup. Now as far as the rest of the country it is standard here to just dial the area code and then the 8 digit number. So I am assuming I would need 2 strings to accomplish this. Any assitance with this I would appreciated.

Thanks DB