Keep playing (one-sided) phone tag with MD

I graduated school last May and am currently stuck in a MO/BO job at a BB (risk and trade clearing). I went to a non-target so it wasn't as if companies were banging on my door looking to hire me, but I managed to find a couple fixed-income trading MDs on the street who went to the same school I did. I cold emailed them and one told me to give him a call; problem is that it seems as if I keep missing him or I call at a bad time. I've called 3 times in the past 10 days -- the first time, nobody picked up, the second time (yesterday), he picked up but in fairness it was literally right after the market went crazy in the last 30 mins of trading (he told me to call back after 5 but I wasn't free), and today I called back again only that he was out of the office. (I know my call wasn't being screened because I was told he was out before I said who I was.) So I shot him an email just to say I'm sorry we keep missing each other and let's try to set up a time, though I haven't heard back yet.

How many times should I keep trying him and with what frequency? I want to keep him warm but I know traders are busy during the day, use Bloomberg more than email, and tend to leave as soon as the market quiets down post-close, so how am I ever going to nail him down?