my parent view model contains couple child view models and it looks like 

```
public MainViewModel:ObservableObject
{
     public MainViewModel(){//initalize everything};

     private SomeViewModel childvm1;
     private AnotherViewModel childvm2;

      public SomeViewModel Childvm1
            {
                get
                {
                    return childvm1;
                }
                set
                {
                    SetField(ref childvm1, value, "Childvm1");
                }
            }

     public AnotherViewModel Childvm2
            {
                get
                {
                    return childvm2;
                }
                set
                {
                    SetField(ref childvm2, value, "Childvm2");
                }
            }

     //when this changes i want to notify childvm2 and call a function in it
     public SomeModel SelectedValueofChildvm1
            {
                get
                {
                    return Childvm1.SelectedValue;
                }
            }
}

```

how can i call a function in `childvm2` when `SelectedValueofChildvm1` changes?