HELP: Pass Variables from Course to Course?

Does any know a way to pass a variable from one course to another? I'm publishing tests inside an LMS and once the tests have been completed, they can access a certificate in a separate course. The certificate should not be able to be accessed if the tests have not been passed.

After a little research on here, I tried creating an identical variable in two courses, setting them to retain values between sessions, but it didn't seem to work. Am I missing something? Or is there something else I should do?

Any input would help. Thanks!