JB12:
I thought that I'd done exactly that with my first post on this thread!
Example:
If I see a guy on the telly who has got a massive fortune, a beautiful wife and a fantastic lifestyle, I could find myself thinking "I wish I was that guy". That's envy
However, if I've been hoping to date a certain lady but I find that she's going out with someone else, I would also feel envy. (i.e. I'd wish that I could also be in his shoes). But because (unlike the rich guy above) he's 'taken something from me', I might also have very negative feelings towards him (possibly bordering on hatred). It's the addition of those negative feelings which turn simple 'envy' into 'jealousy'.