If you want to do this in Lite-C, you should read this thread :

Dijkstra + WED paths

You'll find there :

• how to use paths created with WED to initialize the matrix
• a link to a very basic demo to use it

But you should try to use Alex's algo script rather than mine for best preformances.

Anyway, I am finishing a new free plugin with a demo level to gather all this features. Delay : about 1 or two weeks...