You need to format the column for the payroll number. Click on the column top to select the entire column. Click on Format and choose Cells. The Format Cells dialogue box opens – choose Custom at the bottom of the category list. In the Type: box, highlight what’s in there and type in a series of asterisks, then click OK. Now type a number in the first cell of this column. Press return and the number changes to asterisks. Click back on the cell full of asterisks and the number you typed in appears on the formula bar.
it is fairly simple to change what is in a cell. However, the typed digit would be displayed initially, and I suspect that you do want the underlying "number" not to change, and it is just what is displayed to be asterisks. If so, it is beyond me... though not I suspect others.
I also assume that you wish to be typing into a cell, rather than a form?
This could be achieved via VBA. I have a password entry routine (written by Juan Pablo Gonzalez) that puts up a dialog box. Characters typed into the box are displayed as asterisks as they are typed. It would be possible to adapt this to write to the current cell.
However, data entry would be extremely tedious, even if using a button to call up the dialog box.
I would have thought that Torrisdale's excellent suggestion should suffice.