If you switch between Excel for the PC and Excel on the Mac (either 2004 or 2008), you probably know that there are many differences in the keyboard shortcuts between the two platforms. To make switching back and forth more seamless, you can use Excel's ability (or the system's) to remap keyboard shortcuts on the Mac to match those on the PC (or vice versa, of course). However, there's an undocumented but often-used keyboard shortcut that seems immune to these solutions -- the keyboard shortcut for "edit in cell."
On a PC, you can edit the current cell's contents by pressing F2; on a Mac, it's Control-U (F2 copies the cell's contents). I much prefer the simplicity of F2 over Control-U, however, it doesn't seem possible to customize this shortcut. This "edit in cell" command doesn't appear in any of Excel's menus, nor does it appear in the list of all commands in the keyboard shortcuts section of Excel's customization dialog. Google searching didn't turn up any simple solutions, so I built my own using Butler, although any tool capable of creating macros should work fine.
Open Butler's configuration screen, and create a new Shortcuts item. On the Keys tab, type Control-U, then switch to the Triggers tab. In the Hot Key box, press F2 (you'll see a warning about some programs not responding if you use F2; just click "Use F2 Anyway" to ignore the warning. Change the Exceptions pop-up from Not to Only, and in the text box below, type Excel,Microsoft Excel to specify the programs where this shortcut works. (On my Macs, I had to list both versions of the name to make this trick work in Excel 2004 and Excel 2008.)
That's it; from now on, you can press F2 to edit the current cell in Excel on the Mac.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080712055817205