How can I increase my Time Machine partition size?

A while ago I bought a 3 TB MyBook from Western Digital to use as a backup drive. I have my MacBook set up to dual-boot with Windows 7 through BootCamp, and at the time I thought it was a good idea to partition the MyBook so that I could have seperate partitions for my Windows backups and my Time Machine backups. However, I could never get Windows 7 to actually perform a sucessful backup.

I have since deleted the "windows" partition from the MyBook, and I want to increase the "time machine" partition to fill up the now empty space.

I tried dragging the corner of the partition down and increasing the size through Disk Utility, but I get an error message saying: Partition failed with the error: Couldn’t modify partition map because file system verification failed.

When I run "diskutil resizeVolume disk2 list" in Terminal, I get the message: Volume format does not support resizing

Is there any way I can resize my Time Machine partition without restoring it and losing all my backups?

Thanks,

Jules