visa guidance

i am a Pakistani doctor,working in beijing,but I am more interested to work in Hong Kong.So,for that I have to pass HKMC exam,I had applied for the rejistration of that and i will have my exam on the dates.i.e,
1) 11~19 march 2013
2) 8 ~ 12 august 2013
3) 21~29 nov 2013.

How i can enter hong kong in one year ,3 times ? I had never been there before too ?
which visa should i get ?
is there any visa that i can get for 1 year with multiple entries ???

Kindly do let me know accurately