How Can I make this function to work on a protected sheet (Excel version: 2003)

The Code:

Function LSUser()
LSUser = Environ("username")

End Function

Much appreciated if I could get the answer for this issue :-). The function
works fine on a protected sheet in Excel:2007, In Excel: 2003 it doesn't
changes the name if a new user updates the worksheet. All the cells in the
worksheet are write protected except for some on which the user enters the
information and then saves it. The worksheet was designed and created in
excel 2003.