Ice Cream Sandwich (ICS) - Encryption, select different PIN than Screen Lock
No. A quote from http://support.google.com/android/bin/answer.py?hl=en&amp;answer=1663755:


  Note that this is the same PIN or password that you use to unlock your phone without encryption, and cannot be set independently.


EDIT: I found this on xda, but I think it might be risky and not worth the effort.
http://forum.xda-developers.com/showthread.php?t=1680857