Constraining one point to another for fabrication

I have been investigating how to constrain points to one-another. Specifically the top right corner to the center point of the panel of a attached definition. As the center points moves the corner points shall move equally. I believe that by both points moving equally in space the length of each side shall be equal thus allowing me to unroll the panel into the original equal rectangle. Simply, creating a flat sheet with two breaks in it for ease fabrication/ economy of material. Any ideas?? panel%20testing.JPG

Cheers + thanks...

AB