Sorry - also see below for how to add and use code:
On a sheet tab, right click, then click "view code" - this opens the VBA editor.
(Or hit Alt + F11).
On the menu bar at the top, click on insert > module.
This opens a module in the Active workbook.
(If you want to add code to another workbook, select the file from the project explorer on the left of the VB editor.
(If the project explorer is not showing, hit Ctrl + R).
Copy and paste the whole code snippet supplied, adapting anything to suit.
(Or write your own code)
Save the workbook.
You may need to enable macros.
http://office.microsoft.com/en-us/excel/HA100310711033.aspx#12To run the macro there are a few choices:
http://office.microsoft.com/en-us/excel/HP100141131033.aspxTo add to your personal.xls(b), and thus have the code available at all times:
http://www.rondebruin.nl/personal.htm