It sounds as if you are not understanding a key principle of derailleur operation. The high limit screw serves only to stop the outward movement of the derailleur cage. If the cable is not pulling the cage outward you can adjust the outer limit screw until the cows come home and not see anything moving. Please follow this procedure from beginning to end without skipping any steps; remove the shift wire and proceed as if you were installing it from scratch.

http://www.parktool.com/blog/repair-...ur-adjustments