Dynamic Blocks - Stretching

[how do i do this?]

Hi, I have a box, and inside that box, there is another box. Connecting/joining both boxes are two lines on all four sides of both boxes. What I don't know is how to stretch the outer box (dynamically) from the top right corner, to any size i wish to drag it out to (keeping the inner box in the center at all times, and keeping the lines joining the boxes, conected to both boxes). This puzzles me to the point where I have absolutly no idea what to do.

 

I can:

-Dynamically stretch the outer box from the top right corner, keeping the inner box in the center

 

I can't:

-Keep the lines joining the two boxes connnected to the two boxes.

 

Please help, there is a picture attached that shows the box before it is stretched, and a picture of the end result that im looking for. I just need to know how to dynamically stretch the first image to generate the second image.

[SuperCAD]

My first guess would be scaling the outer box and using chained stretches with different angular offsets to control the lines connecting it to the inner box.

 

I don't have a second guess at the moment...

[dbroada]

I've cludged this together. Not EXACTLY what you are looking for though.

 

CROSS.dwg