if you insert a new button into each workhseet and rely on your personal.xlsb the macro button would still be there if anybody else opens the workbook but will fail as your workbook will not be available. It pretty much would be if you use an AddIn for that type as that AddIn would be addd to the list of AddIns in order to work.
If you press ALT+F8 the macro window will appear. You could assign a shortuct to your macro which would enable you to run the macro from every workbook without instering any buttons but just pressing the combination you choose. I think that to be a better way than inserting macro buttons, assigning macros to them and deletiung them after work in order not to run into run time errors. You could work around by creating a ribbon and inserting the macro there so it would not be run from the personal.xlsb. A start button on the personal.-xlsb doiesn´t make that much sense as that workbook is hidden by default, you could add a new item to the AddIns ribbon part.
Regarding the MsgBox after completion of the macro. Insert the code into a new workbook after inserting the code into a standard module into that very same book and run it: