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

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

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