Not sure exactly what you're trying to do, but can you not plot the Fcurve, or simpler still rather than playing with the Fcurves (which I'm guessing would be one for each point in your model) wouldn't it work simply animating the objects that magnet+ influences....
you may have missed the fact that you can animate the objects to affect the effect (if those spellings are the correct way around 
as I just pulled up an old animation using this effect to check & it took me a while to figure what was happening.
For this method to work I believe you must first animate your "control (magnet) object" then add the magnet effect, tuning the area of influence as needed.
Presumably, though I've not tried this, to further control the effect you may add more magnets and use the DopeSheet to control which is in force at any frame.