Have any chance to get my student (F1) Visa?

in Fall 2009, applied for student visa at 4 times but unfortunately was rejected. Now I am thinking to apply again for Spring 2010. What do you think? have any change to get that? additionally I want to mention that I am from Bangladesh. My sister is living in USA as a permanent resident. Last time the visa officer said me that I will never come back Bangladesh.That is true. But I want to settle myself in Canada or Australia after my graduation. So how can I convince him?