If your laptop has a touchpad mouse (a little pad about where your thumbs are when you type - move the mouse around with it) you can emulate the scroll wheel by tapping once on the right hand side of the pad and, while keeping your finger pressed down, moving your finger up and down the right side of the pad. It's a little tricky to get it right, but better than nothing.
The best thing I did was to spend $45 on a wireless, optical USB mouse. Plug it in the USB port, no wires to crap with, the optical mouse works on most any surface (your leg, arm of a chair, the empty seat next to you, whatever....) I just need to keep a couple of spare AA batteries around for the occasional times it runs out of juice.
HTH,
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