Controlling speed of keyframed animation

With Max 2014 I’ve set up a single bird wing flap with keyframes on a helper object. The out of range type is set to cycle so it flaps throughout time.

I would like to use this helper to control a wing object, but be able to vary the speed, perhaps with another scene object or custom slider.

I tried a script controller but there appears to be no way to call upon another tracks value at a multiple of the current time so I can’t vary the speed of the flap.

Am I missing something in the script controller or is there another method?