Help! Camera Manipulation Limit???

Hi, can anybody teach me how to set a camera manipulation limit? For example: My currently camera is at a Model but i want set the limit that you can scroll your mouse.

My currently code:

cam.CameraSubject = game.Workspace.Camera2
cam.CameraType = "Attach"
cam.CoordinateFrame = CFrame.new(1485.333,3444.659,-9139.552)
cam.Focus = CFrame.new(1494.948,3446.06,-9148.231)

This camera type just can move up and down... i want make it rotate but without move the camera forward or anything like it.

If you set the CameraType to Track, and then set the CameraMaxZoomDistance to the same value as the CameraMinZoomDistance, the camera should be locked to that distance away from the subject. If the Track CameraType doesn't work, the Custom one should.