Add/revise 'meta tags' with Excel 'Script Editor' ???

How to add/revise 'meta tags' with Excel 'Script Editor' ?

When change (using the script editor) the standard Excel-2003 meta tag

<meta name=Generator content="Microsoft Excel 11">

to (or just add as another meta tag line with)

<meta name="description" content="a,b,c & d">

and save, it changes (or deletes added line) back to

<meta name=Generator content="Microsoft Excel 11"> .

Is it not possible to add/edit meta tags for web pages created with Excel ?

Ideas ?