There are rules for valid characters for bookmark names and it appears your code is trying create a bookmark with a name that is considered invalid. From memory, bookmarks can't start with a number, nor can they contain a space for instance. There are probably other rules on what is allowed as a bookmark name.

When you encounter the error and choose to Debug, hover over the StrIdx to see its value and make note of what it says. Do any characters appear to be unacceptable as bookmark names?

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Andrew Lockton
Chrysalis Design, Melbourne Australia