I just noticed you have opened a support ticket regarding the same question. I've already answered you there, however I will copy my reply here in order to be available for the community and will ask to continue the conversation there:
What I can suggest you in order to achieve the desired would be to hook to the MouseLeftButtonDown event of the CustomPane and Pin it there. However as the event is handled in the code you would need to hook the following way:
sender, MouseButtonEventArgs e)
Hope this helps.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.