Is this possible

Unfortunately no, I believe you will have to dump the Boot Camp partition and start over.

 

I think this may be possible; however, I'm not sure if the second part is accurate as I have not tested this myself, so please check around before attempting.

I'm thinking it would go something like this:

First, using a 3rd party hard drive manager in Windows (such as, Partition magic), partition off however much you want to place back to your Mac.


Second, go back into OS X and try the following:

1. Open Boot Camp Assistant, in the Utilities folder in the Applications folder.

2. Click “Create or remove a Windows partition.” Click Continue and select the disk you partitioned off in Widows. Then select “Restore to a single Mac OS partition.”

 

i've done the opposite where i wanted to expand my bootcamp partition. successfully used this free software to do it: http://www.paragon-software.com/home/camptune/

only thing with this is that you have to burn it to a cd, boot off of it, and then make the changes.

i've heard other people using gparted and i think with that you can just do it right in the OS.