Hey pg, another way to do it is use the extension dialing capability built into the bb:

In the phone number field for the person you are calling type the number like this:
1-800-555-1212,x2000

This will first dial the number, pause, and then a popup screen will appear asking if you want to dial then extension, skip, or end the call.

You could very well enter it as follows:

1-800-555-1212,xLARRY

Just another way to skin the cat. Unfortunately, this will not allow you to dial multiple extensions (ex: 1-800-555-1212,1,xLARRY)