Relative easing in Actionscript?

So Im wondering if there is an equation for easing to a position relative to its native position using AS. For example, if i want a Symbol to move 100 pixels up from it original position. Is there a way to do this without knowing the Symbols original position?

Heres what I know:
The"non-relative" easing equation in AS is:

myClip._y += (-100-myClip._y)/speed;

This is all well and good, but it assumes myClip is located at 0

Here’s what I tried to do:

myClip._y += ((myClip._y-100)-myClip._y)/speed;

This did not work at all. It just started going up forever.
So, is there a way to ease something without knowing the Symbols original position?
I know Im missing something. Any help would be great
Thanks!!