Restricting input to NSTextViewCell inside NSMatrix

Objecive-C/Cocoa newbie...I have an NSMatrix composed of NSTextViewCells.开发者_如何学Go I would like the user to be able to type at most one letter into each cell, have the letter upcased if necessary, and automatically tab to the next field.

It looks to me as if I can use an NSFormatter to do the upcasing, but I can't figure out how to get the auto-tabbing.

Is it just me, or is the available documentation in general less than wonderful? I've been reading Hillegass' book, which is great, but it only goes as far as it goes :)

Thanks.