External Bind Inside ListView

Hello.
I have a ListView that has the property ItemsSource with a list. Everything works ok, but i need in ViewCell make a bind that have a appointement out of ListView ItemSource.
I try made in this way: {Binding BindingContext.DeleteText}, but not work.
I did some researches and i found the property RelativeSource, but i found in some foruns that this property not work in Xamarin Forms.
How i can use the bind referencing a item that don't exist in object that i referencered in ItemSource property?