Hi,
The refresh button is no longer on the Command bar in IE7. It is pernamently on the navigation bar (Address, Stop, Refresh, Search).
To replace the nav bar with a customizable toolbar see http://www.quero.at (does not have IE7 anti-phishing and secure site features though)
For a replacement 'Refresh' command bar button see http://www.iecustomizer.com/?url=iebuttons (the site is down at the moment so I don't have the exact link for you, but search for Refresh should find it for you). This is a scripted button and does not work all the time (the document has to have focus, click on the document before pressing the refresh command button).
Best to stick with what IE7 is designed to do. Most modern keyboards now have special web navigation buttons and the newer mice have customizable buttons that you can configure to whatever function you want. F5 is easily pressed while the right hand remains holding the mouse.
Regards.