Excel - InputBox control....

I have an Excel program that is controlled via macros written in VBExcel. This program has 15 users. When the program is first opened, a menu pops-up (Via the InputBox command) that lists all 15 users. The user then "tells" the program who he/she is by entering the number that is next to his/her name in the InputBox. Users can then create their own password, or, if they already have a password, they can change it. But, I can't find a way to "hide" their password from someone that might be looking over their shoulder. I would like to have asterics show up instead of their actual password, the way Excel does it when you have a workbook that is password protected. Anyone know how, or if, I can do this?