Linking between base docksite and parent docksite.

Hi,

How to link the base docksite and the parent docksite when i am using the PrismIntegration with docking concept.

Means I have one  parent docksite and some child docksites in that parent docksite and these child docksites acts as the region which are registered and filled using PrismIntegration and MVVM and Docking concept.So how  i can link these any of the child docksites with the parent docksite. 

ForExample:

<docking:DockSite x:Name="BaseDocksite">

<docking:DockSite cal:RegionManager.RegionName="{x:Staticsample:RegionNames.MainRegion}">

</docking:DockSite>

<docking:DockSite cal:RegionManager.RegionName="{x:Staticsample:RegionNames.MainRegion1}">

</docking:DockSite>

<docking:DockSite cal:RegionManager.RegionName="{x:Staticsample:RegionNames.MainRegion2}">

</docking:DockSite>

<docking:DockSite>

Above example shows that there are three docksite registered  and filled with the docking windows using PrismIntegration with docking  and  MVVM concept.

I want to link the docksite named MainRegion with the BaseDocksite. But its not linking properly.

So how to link Basedocksite with child docksite.