Property value is not set and call back method is not invoked - Windows store apps

Hi All,

I have a dependency property of type object with default value 0.0 and a property changed call back method for it(custom control).

When I set it's value (two way binding nullable int property) as 0 or null, property changed call back method is not called. It's value remains as 0.0. This doesn't happens when I set some other value with binding and for all values(including 0,null) without binding(through xaml or c# hard coding). I would like to do different actions for the values 0 and null. How can I get notified?

Any help would be greatly appreciated.

Thanks,
Jessie