theres no way to repair the cable, you need whats called a window regulator, it comes with new tracks, motor and the cable. cost about 50 on line or less used.
Do this. You are better off replacing the entire thing.
1999 GP GT 18" Boss 353 Concave|SLP CAI|Borla Cat Back|Plog|HV3|HV TB|ER Rockers|Custom Retrofit Projectors|GMPP Lowering|GMPP Handling|MPD F1|Full Diode Dynamic LEDs