Good information about various COE melting points in this thread:
http://www.wetcanvas.com/forums/showthread.php?t=258093
You would need to put a straight piece of glass suspended across something in the kiln then increase the kiln temperature until you see the piece start to droop. Do that for each COE and your dicro and see which temperature matches the temperature at which the dicro begins to droop. (And I would try to make sure the thickness of the glass pieces are the same.) That should give you an idea of the COE. I haven't ever tried it, but in the imaginary world of my mind it works. Hope it helps! Let us know if you try it.
(And if I'm totally off in my own little world, someone please correct me so I don't lead anyone astray.)