MsgBox "****YOUR CUSTOM MSG, DISPLAYS ON POPUP BOX", vbSystemModal
I use this to notify me to have some water. Genarally we forget to have water at office. So Created a file with is line having msg saying "take some water". Now using crontab(linux)/schedule tax(windows). You can schedule say for every hour. So that you will get popup every hour reminds to have some water...
how to add task to scheduler.
http://www.7tutorials.com/how-create-task-basic-task-wizard (wizards may varies but you can get idea)