Extending a B1 Visa for Medical Training

Hi
I have a clinical rotation for one month at a medical school starting from 5th of jan and ending in 30th of Jan
B1 visa was issued from 1st of December ending on 25th of February

I just received another acceptance letter for another month ending on 27 of Feb
I also have another letter from the ECFMG to do medical exam which depends on a calendar which is busy till may

can I extend my stay at the port of entry beyond 25th of Feb??

i am asking becase my friends didnot fill the I 94 for their stay for this short visa. they just get a stamp of entry and the stay is depending on expiration date of the visa

the following is my friend's case:

http://i58.tinypic.com/1xyr6p.jpg

http://i58.tinypic.com/21mg8dy.jpg

A visa allows you to apply to enter the United States by presenting yourself, your passport and visa at a port of entry. Your duration of stay is not defined by your visa -- it is defined by your I-94.

To file to extend your stay beyond the initial, authorized period, you may leave the U.S. and attempt to re-enter, or you may file Form I-539, (Application to Extend/Change Nonimmigrant Status) along with all required supporting documents to the USCIS.