Done!!!!

I have created a public delegate:

    public delegate void EntityListChangedDelegate;

Then in the ABusinessObject class of my business project I added an event:

    public event EntityListChangedDelegate EntityListChanged();

and overrided the OnStateChange Method addingode to fire the event when retrieved:

    if (bizState == mmBusinessState.Retrieved)
    {
        if (EntityListChanged != null)
        {
            this.EntityListChanged();
        }
    }

Now in my WPF Window I added to the constructor, after registering the object:

    this.bizObj.EntityListChanged += new EntityListChangedDelegate(bizObj_EntityListChanged);

Then in the method created I added the code for setting the ItemsSource of the grids:

    this.dataGrid.ItemsSource = this.BizObj.EntityList;

Now I don´t need to keep track where and when an object has perform a GetEntity or GetEntityList, the grid is updated automatically. I only need to set the grid´s ItemsSource for childs when a new entity has created for a parent bizObj.