New Post: CustomProperties in Excel (.xls): issue name and value in unicode, should be UTF-8

I want to add name-value pairs in the CustomProperties of an 97-2003 (.xls) Excel spreadsheet. Adding works, but name and value are inserted as unicode. The name is not not readable anymore (look like chinese characters).
Name and value pair should be UTF-8 (single byte) for correct use in Excel 97-2003.
Does anyone have experience with this?