non valid parts from wall

Hi everyone,

I'm trying to get the true Area from wall parts.
I've done it dividing the parts' volume by their height and assigning it to a new Shared parameter.
The problem is that Revit still reading "non valid parts" (original parts from dividing parts).

Is there a way to identify the original parts to exclude them?

 // Get parts surface
        foreach (Element el in docCollector)

        {
            Parameter exclusion = el.LookupParameter("Exclusion");
            int elexclusion = exclusion.AsInteger();

            if (elexclusion == 0)
            {
                Parameter volume = el.LookupParameter("Volume");
                double elVolume = volume.AsDouble();

                Parameter hauteur = el.LookupParameter("Hauteur");
                double elHauteur = hauteur.AsDouble();

                double elArea = elVolume / elHauteur;

                Parameter PPArea = el.LookupParameter("PP_Elements_SURFACE");
                PPArea.Set(elArea);
            }
            if (elexclusion == 1)
            {
                Parameter PPArea = el.LookupParameter("PP_Elements_SURFACE");
                PPArea.Set(0);
            }
        }