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>Or, what we already had.

I was sure that I've seen something like I've done, but I didn't remember :). Too late.
I was ispired by free Office Accounting 2007 interface. You can see this "grid footer" all over the place. There are more nice UI stuff there, the next in my pipeline is the group bar.

The "funniest" part in my class design was LockColumns support, though.