Could anybody tell me how to do that:
at start of game, you can research all techs (this I can do)
What I can't do, is
each time a tech is researched, another one is randomly removed from the global list, so I can't research it anymore...

thanks in advance for your ideas or bits of programming.....

That is liable to be very complex/deep. I don't think this is going to be a trivial X=B+A kind of fix.