you have to replace the whole palm rest.  Click the reference link at the top and go to user guides.

I recently had my whole Palm rest replaced.  It may have been the result of over heating in my system, since it was alwyas really, really warm.  In either case, I did have to have it replaced because it became unresponsive.  I thought it was due to some changes in my settings or a virus, but it was not.  Is your mouse pad acting like it is sticking?