I need to connect iPad 2 64GB 3G/WiFi via tether to MacBook Pro 17 i7

I need to activate, initiate or install the ability to tether on iPad 2 64GB 3G/WiFi. I work with "Doctors Without Boarders". I travel with a MacBook Pro 17" i7 and the iPad 2. I am at times in places where network via WiFi and RJ45 Ethernet is unavailable. In those places I've found that I've had constant Internet accessibility via the 3G radio in the iPad 2.

IPad 2 sold in Europe, in this case Spain, are unlocked and unencumbered by carrier contracts. You can even purchase a single day of 3G access. While it is possible to access the Internet at all times via the iPad 2 the device is not powerful enough to be used for the medical calculations I need to make in the field despite it's ability to access the Internet, a task perfectly suited to the MacBook Pro 17" i7.

I need the MacBook Pro 17" i7 to access iPad 2 3G/WiFi via a tether so It can access the Internet using the iPad as the wireless router. Is there anyone out there who can tell me how to achieve this?