an ellptical trainer is a piece of gymn equipment that has zero
impact, otherwise known as a cross trainer. I am looking for a
graduated workout program. has to be interval based.

There are a couple of pages on interval training at about.com. These
are written for treadmill use but can be modified for an elliptical
trainer.

http://exercise.about.com/library/blbeginnerinterval.htm
http://exercise.about.com/library/cardio_workouts/bl_cardio_intense.htm
http://exercise.about.com/library/cardio_workouts/bl_cardio_endurance2.htm

A general explanation of interval training can be found at
http://www.fitness-advantage.com/fitness-exercise/interval-training.html.

The idea is, after warmup, to have short bursts of high intensity
exercise (achieved through raising the resistance and/or moving
faster) followed by periods of active recovery (moving at a more
'normal' rate/restistance so your heart rate lowers but doesn't go
completely to resting).