Eric Wahl, a 42-year-old millionaire Manhattan advertising executive, thought he made a date for sex with a 13 year old girl he met on the Internet but his alleged date turned out to be a girlish-looking undercover female detective.  He told the girl to wear her school clothes for their rendezvous.  When they met in Greenwich Village last October and he took her to a nearby hotel room, paying in cash under an alias, he ended up getting handcuffed, fingerprinted and arrested on charges of disseminating indecent material to minors, attempted sodomy, attempted sexual abuse and attempted endangering the welfare of a child.  He is just one of a growing number of alleged Internet prowlers nabbed by New York Police Department's cybercops.  These dedicated undercover detectives prowl the 'Net looking for pedophiles.  According to the New York Post, thousands of pedophiles prowl chat rooms devoted to kids' pursuits and hobbies.  Often they target kids whose responses suggests they are lonely, depressed or alienated, clear signals they are vulnerable and could be receptive to a solicitous adult.  Pedophiles may also hook up with teenagers who stray, either by mistake or out of youthful curiosity, into a chat room geared to adults.