VBA GetUserName

I have the following code to get user name. I don't know how to add user name to one cell and have it locked and add another user name in another cell and have it locked when they open it to verify. Is it possible?

Sub Username()
Function GetName(Optional NameType As String) As String
     'Function purpose:  To return the following names:
     'Defaults to MS Office username if no parameter entered
     '
     'Formula should be entered as =GetName([param])
     '
     'For Name of Type       Enter Text  OR  Enter #
     'MS Office User Name      "Office"        1 (or leave blank)
     'Windows User Name        "Windows"       2
     'Computer Name            "Computer"      3
     

     'Force application to recalculate when necessary.  If this
     'function is only called from other VBA procedures, this
     'section can be eliminated. (Req'd for cell use)
    Application.Volatile
     'Set value to Office if no parameter entered
    If Len(NameType) = 0 Then NameType = "OFFICE"
     'Identify parameter, assign result to GetName, and return
     'error if invalid
    Select Case UCase(NameType)
    Case Is = "OFFICE", "1"
        GetName = Application.Username
        Exit Function
    Case Is = "WINDOWS", "2"
        GetName = Environ("UserName")
        Exit Function
    Case Is = "COMPUTER", "3"
        GetName = Environ("ComputerName")
        Exit Function
    Case Else
        GetName = CVErr(xlErrValue)
    End Select
End Function