Open a new window in an existing window

Hello,

 

I have a special thrid party control (from synfusion, it uses an "SampleLayoutWindow" if anyone encountered that) that seems to act like a window, meaning that it`s the highest in the hierarchy so no other control can host it as it`s own child..

 

What I want to do is open a window in the same "Frame" of the existing window without poping the new window on top of the old one.I can`t use user control since this control needs to be in the highest hirerachy ,as said..

 

Is there a way to open a window in the same "visual frame" of the existing window like all modern programs do ?

 

(I don`t want to use tabs since it doesn't look aesthetic at all).