Excel doesn't support anything like this when you're entering data into a
cell.

Just to add to Dave's statement...

Even if you could set up a format to mask the display in the cell, the true
value would always be displayed in the formula bar... that is just the way
Excel works. Accepting passwords (what I think you [the OP] are asking for)
is not something a worksheet was designed to do. The suggestion to use a
UserForm is the way to go.

Rick