My pen has 2 buttons where my pointer finger rests (which is pretty standard AFAIK) and I setup the button closest to the tip to be MMB (and the other button RMB). That enables me to easily rotate, pan and zoom when using the pen + tablet.
Thank you for the response. This solution will work with my Wacom. It wont work with my HP Stylus because I seem to be unable to setup a button to act as MMB. I will contact HP for this. Thanks again!