If you want the Excel file to be external (and editable), you
can embed it with the parser function from Microsoft. You would
simply have the link as <A ONCLICK="parser('yourfile.xls')"
STYLE=text-decoration:underline; COLOR: green; CURSOR:
hand">Your link text</A> and then insert the parser
function, shown below, into your HEAD section.
The Excel file must be in the same folder as the CHM file,
and the user can edit the file, which could be a drawback.
My old version of RoboHelp removes this function in the
WYSIWYG editor. Hopefully newer version won't do this. This
function is necessary to find the path of external files and was
included with the very first release of HTML Help.
John