Remind user every 30 minutes to update active workbook

Hi to all,

I hope everyone of you here are OK. In my post, I am having a problem on how can I remind user to update a specific active workbook every 30 minutes(that workbook is all about documenting his task for today with log in and log out system), I am using Application.Ontime command but it seems it doesn't work. and take note that the user will unable to save or close the workbook if the user didn't consume 8hrs of working hours(which is I did this part already).

Appreciate your great help, thanks in advance.

Up for this:-)