I have heard of cases like this working. Instead of just calling to tell them you are interested you should really call them to update your file. For instance, tell them you want to add 100 more hours to your shadowing, etc.Maybe you can call a few times (not like anything excessive to seem annoying) but to show that you are extremely interested in the program. So when a seat opens up, they will remember that "Oh, this person seemed genuinely interested" and maybe consider you and call?
Only an idea!