There is no Excel Function that will convert numbers to text as you wish.
You must use a User Defined Function such as you find at the site Nick has
pointed to.
You copy the UDF to a general module in your workbook and it will show up in the
User Defined list under Function Wizard.
Couple of other sites can be found on Bob Phillips' site.
http://www.xldynamic.com/source/xld.xlFAQ0004.html
Note the Add-in by Laurent Longre.
It will add a function to Excel when loaded through Tools>Add-ins.
Gord