A young girl was forced off an elevator and sexually abused in Harlem in the latest sexual assault of teenage girls in Manhattan and the Bronx.  Police are seeking a suspect in connection with as many as nine knifepoint sex assaults.  He struck a second time hours later a short distance away in the St. Nicholas Houses.  The attacks target girls age 12 to 16.  He is described as a thin, black male, about 5 feet 6 with very dark lips and a lazy left eye that appeared to be slightly shut.  There is a $2,000 reward for information leading to his capture and conviction.  Police ask anyone with information to call 1-800-577-TIPS or Manhattan Special Victims Squad at 212-694-3010.  All calls are kept confidential.