IF MOUSECLICK()=1 returns true if the left mouse button is clicked, IF MOUSECLICK()=2 returns true if the right moust button is clicked.
Not going to get into any code here, there's a lot of ways to do waht you want but one of the simplest would be to create a "dummy" object, add a limb to that object, offset it on the z and y axis to the distance and height you want the camera, position the camera at the limb's position, point the camera to wherever, then rotate the dummy object left when the right mouse button is clicked, and vise versa when the left mouse button is clicked.
Just a note usually when creating "dummy" objects (by this I mean just any object that wont be seen by the user, usually the user won't even know its there), you should make them triangles with dimensions 0,0,0,0,0,0,0,0,0 and then proceed to hide them for the smallest amount of lag possible.
There's been a lot of questions on rotating the camera around a point, some searches would bring up a lot of examples, I think I even made a commented-snippet to someones question on the topic, just glance around in the search and you'll find an example somwhere.
Goodluck,
- RUC'