Your workbook is configured for 64bit Excel.....which I currently don't have access to cos I've left my surface pro in the hotel. This means none of your code works for me, so I can't have a proper look and don't have the time or patience to convert to 32bit.....however.....for multi user interfaces in Excel you need to have your UI workbook set as a 'Read Only' file so all users can access it. Everything the UI does is then written to whatever data source / store you're using with checks in the code to ensure read / writes succeed.

Do not even think about using Excel's 'shared workbook' functions.