Isn't it ironic?

I have a "friend" at the moment who I started spending time with when we decided to work on a project together. It started off quite well and we met up and got a fair amount of work done. We'd also meet up at the weekends sometimes. This was when he was between years at university and when he went back to do his final year we'd still meet up but the project took a back seat and I spent my time helping him with his coursework.

Now I'm a pretty generous person I think, even with my time. I don't mind helping people but I soon started to learn that computers weren't this guy's thing. No matter how often I'd tell him something he'd never learn it. I wasn't helping him with his coursework, I was doing his coursework. At times I'd deliberately leave things half done and gave him direction and advice about how to finish them but he never would, he'd just hand in what I'd done, half finished and all. He promised he'd work on things through the week but never did. I began to really resent it as I could be having down time or doing overtime myself but instead I was giving up my time for nothing. Then he'd start putting all these pressures on me if he had a deadline and would want my help more and more. Then times I'd go to help him and he said he couldn't be bothered working that night so we'd just watch TV or something instead. Why couldn't he tell me these things before I went over? I was often putting my own things off to give him my time.

After his course was over we'd still see each other at weekends, but when we started working on the project again he'd always arrange to meet and then cancel on the day, and I only saw him when we were working on the project. Now he has a job himself and I give him advice and stuff, but now when I go over to work on the project he wants me to do his work! Work he is being paid for! He doesn't want to let them know he can't do the work so thinks he can get me to do it for him and him pass it off as his own. I showed him some stuff this week and he still doesn't understand any of the basics, he hasn't learned a thing in all this time. He sent me a message saying he could really do with my help this weekend. In other words, he went to work after I showed him what I did and he couldn't advance it on his own so needs me to give up my weekend to do his job for him.

The truth of the matter is that I've kind of had enough really. Yeah it's ok seeing him at the weekend some times but he only does it to keep me sweet, and sometimes brings his laptop for me to "show him some things". I could do without giving up the little spare time I have during the week when I'm snowed under with my own work and could do with doing overtime instead. I can do without him begging me to give up my weekend for him when I need to use the time to relax instead. I'm fed up helping him and him never learning.

What I really need is to sever the whole friendship but I know I won't be able to. Usually I can't keep a friendship going for the life of me, but now I have one I can't shift. I know it's not really a "friendship" though; I know he is just using me and wants me around as I have a purpose. I know that if I just broke off contact he'd keep calling, emailing and texting asking what’s wrong and can we meet up. And I know that I'd relent because I'm weak.

So basically I need some form of exit strategy. I'll try repeatedly cancelling our arrangements and see if he gets the message but I'm sure he won't. As I said, he needs me to do his work so I'm sure he'll be quite persistent.