calculation vertex position from animation to bind pose

Hi all! I am trying to write a script for 3DS Max, for the extraction of morphs for the skin.
Calculating the skin vertex position is simple:

i-vertid
n-boneid
v =vpos[i]* inverse bonebind[n].transform* boneanim[n].transform* weight[i][n]

but I do not understand how to get the top misunderstood by transformation back from animation in a bind position.

restorevertbindpos=vpos[i]* inverse boneanim[n].transform* bonebind[n].transform* weight[i][n] 

http://i.imgur.com/HIcFpKY.gif

this does not work. How to transform in the reverse order, in the same point?