Cmd+T may be a OS X shortcut so you might want to look in the Mac Preferences > Keyboard to see if the operating system would prevent you from using that keyboard combination. Is there an equivalent in Office for Mac? If you continue to use this site we will assume that you are happy with it.
The F4 key in Excel for Windows is normally a shortcut key to Repeat the last command. You can access Excel from many devices with a Cloud-based Virtual Desktop or share Excel files on SharePoint Cloud services? Awesome little addition to the system prefs! For instance the above procedure was done in Excel 2011, but my Excel 2008 version of Excel for Mac wasn’t affected and has to be done separately.
I used to have to google “F4/F2 shortcut in mac excel” every time I needed such shortcut.