The '?' in abcd?efgh should be a legal name of Name.

However, the document in

https://support.office.com/en-US/Article/Define-and-use-names-in-formulas-4d0f13ac-53b7-422e-afd2-abd7ff379c64?ui=en-US&rs=en-US&ad=US#bmsyntax_rules_for_names

does not see '?' as a legal character.

After tried on Excel 2007, '?' is legal so we should allow '?' as well in define Name.