See here with regard to Excel and Appinventor
If you use Google Sheets instead, you can program (using blocks and google apps script) for each user to have their own private "sheet" in a spreadsheet, or to have their own private spreadsheet, but these would be run under your google account.
It gets (much) more complicated if you want them to use their own google drive...
It will all depend on how private you want things to be.