want2transfer

i'm a 2nd year grad student and heard that a professor at another university is working on a project that highly interests me. not only that, but he is looking for a grad student with my particular expertise. i really want to transfer to this grad program now and i am writing a letter to him right now. but i am at a lost on how i should word the letter. any thoughts? in the end, i want to know if he would be willing to take me on and i don't know how to say that. another complication is that i applied to his department before, but was rejected (he was not on the admissions committee however). thanks.