using data till till the 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