VBA change level number of element

Hi everybody ,

I'm trying to change the level number of a element by this way :

el.Level.Code = 0

But when executes this line I have the error :

err.Number

-2147221504

err.Description

El número de nivel ya se ha utilizado (in english , The number of level has been used).

Any idea of what can be the problem , or another way to change the level number of a element ???.

Thanks for your help , regards !!!