Public Sub Mayuscula()
    Dim celda As Range
    
    For Each celda In Selection
        celda.Value = UCase(celda.Value)
    Next
End Sub

Public Sub Minuscula()
    Dim celda As Range
    
    For Each celda In Selection
        celda.Value = LCase(celda.Value)
    Next
End Sub

Public Sub PrimeraMayuscula()
    Dim celda As Range
    
    For Each celda In Selection
        celda = UCase(Left(celda, 1)) & LCase(Right(celda, Len(celda) - 1))
    Next
End Sub

Public Sub VariasMayuscula()
    Dim celda As Range
    
    For Each celda In Selection
        celda = Application.WorksheetFunction.Proper(celda)
    Next
End Sub