Remote registry change

I need to make a registry change to over 300 NT workstation’s, I cannot put a call to a .reg file in the logon script because almost none of the user’s have admin right’s. Does anybody know how to do this without going to all the machine’s because it has to be done in the course of one weekend and that is just a pain to do on over 300 machine’s. No we don’t have SMS and no third party software because the company is cheap. I am pretty sure there is no way but I thought I would ask anyway.