Using Excel VBA you can get the username of the person logged into the computer and print it to a cell.
I have used this before to monitor which users on a network where accessing a staff performance system. I won’t publish the full code, but just the section that gets the username.
So, the code below would be entered as a new module. Note, it is just one line of code to get the name and print to the cell.
Public Sub Get_UserName()
Cells(1,1) = Application.UserName
You could add in an extra line of code to then get the computer name of the computer the person is using.