adding spells to an item is nothing at all like adding feats to an item, i've tried doing a similar thing. i tried adding the droid carbonite spell to a lightsaber and it didnt work, and just to troubleshoot i tried adding a personal sheild and force lightning which also didnt work.
the best i was able to do with the carbonite projector was make it behave like tk102's flamethrower, meaning you can't target manueally it will lock on to the closest baddie. if this works for you i suggest you check out this thread:
http://www.lucasforums.com/showthread.php?s=&threadid=125738)
something that is also noteworthy about this process: the icon for whatever spell you add to the lightsaber will be the icon for your lightsaber and will appear in the armbands menu (assuming you use the same process as tk's flamethrower) and finally and most perplexing of all is that the lightsaber icon will only appear there if the lightsaber is in your inventory but not equiped on your charactor if you try to equip it icon goes away.
good luck to anyone else that trys to make this work, i'm currently still working on it, with no more progress as of yet... the key may be "requireitemmask" in spells.2da