TYLER SAMUEL LEE is undecided about pursuing a career as a full-time creator of cartoon story lines - even though his original story and voice-over will be featured on tomorrow night's installment of the three-time Emmy-nominated animation series "Dexter's Laboratory."

You see, Tyler is only 7 years old. A second-grader at Chatterton School in Merrick, he also takes violin and acting lessons. And although he hasn't received any bookings for Carnegie Hall or Broadway yet, there's time for that. A natural ham, Tyler admits he wouldn't mind going into show business. But for now, he's happy just to make up cartoon stories.

"Dexter's Lab" was his favorite Cartoon Network series even before Genndy Tartakovsky, creator, writer and director of the show, decided to produce Tyler's story for the show's 50th episode tomorrow night.