Excel - AYUDA URGENTE POR FAVOR !!! NOMBRE DE USUARIO EXCEL !!!

Public ShowNameUser As Boolean

Public Usuario As String

Private Sub Workbook_Open()

    ShowNameUser = True

    On Error Resume Next

    Usuario = Application.UserName

    MsgBox "Bienvenido al Sistema de Control de Atención al Usuario, " & Usuario

End Sub

Private Sub Worksheet_Change(ByVal Target As Range)

    If ThisWorkbook.ShowNameUser = True And Target.Address = "$A$2" Then

        ThisWorkbook.ShowNameUser = False

        Cells(1, 1).Value = ThisWorkbook.Usuario

    ElseIf ThisWorkbook.ShowNameUser = True And Target.Address = "$A$1" Then

        ThisWorkbook.ShowNameUser = False

        Cells(1, 1).Value = ThisWorkbook.Usuario

    Else

        ThisWorkbook.ShowNameUser = True

    End If

End Sub