how to dial another phone's modem thru bluetooth


Hi guys,
i really need a way to use from HTC Desire the data plan from the other phone that i have ... (if someone is curious the idea is that my data plan is ok when i'm in my country but when i am abroad i really prefer to use my other phone's data plan)
so, what i need is a way to connect from my htc (as i would from my laptop) to the DUN service from another phone's modem.
could someone please help me with a hint ... like an application or anything that could solve my problem ...