I am using a some excel sheets located on a network server and would like to
make it so one of the fields lists the logged in user as soon as the sheet is
open. I found this VBA Macro in one of the past posts:

Function UserName()
UserName = Environ("UserName")
End Function

This function displays the user but does not auto update when I open the
sheet. I have to double click on the name for it to update the user.