You can get the zone in which the dock is dropped with the get_dockZoneID
method at the OnClientDragEnd
client event, for example. I suggest you the RadDock Client Object help article
You can make the RadDockZone get highlighted when dragging a dock in it. Using the HighlightedCssClass of the RadDockZone you can specify the highlighting style for each docking zone as it is demonstrated in the Zone Highlighting online example
If the above suggestions does not answer the requirements of your scenario, please, send us more details about what you want to achieve so that we can get a better idea of your scenario and do our best to help you.
All the best,
the Telerik team