Dynamic Content of Contentcontrol + change of gridsplitters

hi!

i would like to have the following window.

in the left side there is a content control with a treeview.
on the right side there is on the top a content control (tab control) depending on the selected type of the treeview on the left.
and on the right side at the bottom there is a content control (tab control) depending on the tab selected on the top right side.

i figured out how to dynamically load the content control (tabcontrol) on the right top side. but how do i load the tabcontrol at the bottom of the right side?

the next thing is how can i change the gridsplitters?
now there is one between the left and right side and one one the right side between the top and bottom content.
i would like to add the possibility to switch between left / right (top/bottom) and Left / middle / right.

regards vario