How to know when Binding of property is changed

The following code is used to directly set value of property that is bound to control's property. (In my case a property is bound to ValueProperty of Slider).

private Action<double> _valueSetter; // target property setter cache

private double _newValue;

protected override void OnThumbDragCompleted(DragCompletedEventArgs e)
{
    if (_valueSetter == null)
    {
        var bindingExpr = BindingOperations.GetBindingExpression(this, ValueProperty);

        var property = bindingExpr?.DataItem
            .GetType()
            .GetProperty(bindingExpr.ParentBinding.Path.Path);

        _valueSetter = (Action<double>)property?
            .GetSetMethod()
            .CreateDelegate(typeof(Action<double>), bindingExpr.DataItem);
    }

    _valueSetter?.Invoke(_newValue); // as fast as possible!

    base.OnThumbDragCompleted(e);
}

The problem is if I change the Binding of the ValueProperty I don't know that happened and therefor my _valueSetter is still referring to old property setter.

Obviously one way is to always use reflection without using _valueSetter but is there better way? It would be really nice if I knew that ValueProperty is just bound to new property and then I could update my _valueSetter.

I tried to create another binding for dependency property but they are static and that confuses me. is there any way to fire an event when binding of control's property changes?