More help with Microsoft Excel?

Now I have a list of numbers from 1-8 on column B. Is there now a way for the program to count the number of decisions between each occurrence of "1" and output it into Column C?

Example.

B....C
1.......
1.....1 (Counts from last 1 to the next one and outputs the result)
2.....
3.....
5.....
6.....
1.....5
2.....
3.....
1.....3
7
8.....2 ETC

Can this be done?

Thanks.