Change of status from B1 to F1

[msk200412]

Hello,
I am currently living in Egypt. I have B1/B2 visa and I am going to apply for F1 visa to go for medical training in October and November after few days in the American Embassy in Egypt. The problem is that I need to stay in the US for 2 months prior to my training (August and September). I am going to enter the US while having 2 visas (B and F) and I am going to use B for that entry. But then after 2 months I need to be using my F1 visa for the university. And after I finish my training with F1 visa I will need to stay for more 2 or 3 weeks. So I need to know how I am going to change the status of B to F then again to B (which both I have before entering the US) while I am inside the US because it doesn't make sense to re-enter for 2 times during my stay and it will cost me so much.
Thanks in advance.

[msk200412]

Any help would be much appreciated people

[inadmissible]

Can you take a quick trip to Mexico or Canada and return on your F visa? You'll need MX/CA visa to do so, but it is probably far cheaper than airline travel back to your home country. Cheaper than an in-country change-of-status too, which wouldn't be approved quickly enough for your needs anyway