Excel 2007 : using data till current row

Hi All,
here is what I would like to do :-
Suppose I have the following :-
type p 1-p
1 1 0
2 0.5 0.5
1 0.67 0.33
1 0.75 0.25
2 0.6 0.4
1 0.67 0.33
2 0.57 0.43
1 0.625 0.375
2 0.56 0.44
2 0.5 0.5
1 0.55 0.45
2 0.5 0.5
2 0.46 0.54
1 0.5 0.5
1 0.53 0.47
1 0.56 0.44
2 0.53 0.47
1 0.56 0.44
1 0.58 0.42
1 0.6 0.4
1 0.62 0.38
1 0.64 0.36
2 0.61 0.39
1 0.63 0.37
2 0.6 0.4

So essentially p = (# 1 in type until that row) / (total # of types until that row) .
I have calculated the p's manually. But for a very large data set, thats just not feasible.
Can anyone suggest how to use any function or program to do that in excel 2007 ??????
Thanks