Here's the situation. i got a friend, "Dave", who really likes this girl. he acts really different whenever she is around, only paying atention to her and forgetting about everything else. he also drops everything he is doing the minute he thinks he has even the slightest oportunity to talk to her or see her. thing is, the girl is not interested in a relationship and Dave knows this. he does not actively pursue her by hitting on her or asking her out but i am pretty sure that the girl, along with everyone else either of them talk to, knows he likes her. also, i seriously doubt he will ever ask her out because the only two girls he has asked out said no and they do not really talk anymore. (this makes it really hard to talk to him about her because he is kind of sensative.) ordinarily i would not get involved or even be concerned as it is none of my bussiness but:

1) his obsession is affecting his studies. he is taking two AP tests this year and he has skipped out on nearly all the extra study sessions his teachers have set up.

2) he makes it very awkward for anyone, myself included, to hang out with him or her when they are both there. as they are both my friends and we do hang out rather frequently, this is really annoying.

i have tried to talk to him about it but he just sees it as me being nosey and ignores whatever i say. is there anything i can do or do i just have to deal with it until he gets over it?