As Frenchy explained, "Flow" is the way you could use.
But you have to understand how it has to be used.

The first step is to read the command reference because Flow use curves or surfaces for source and target.
If you use curves, you must use a curve for both source and target.
And if you use surfaces you must use surfaces for both source and target.

http://moi3d.com/4.0/docs/moi_command_reference8.htm#flow

Warning, sometimes surface has to be use and sometimes curves are better way.

Use Flow, practice it, practice it and practice it again !
Because it's a very important tool in MoI toolbox.

Have fun using MoI !