Difficult Count if or Sum if problem

Hi,
I have a 'calendar' sheet where a "1" is inserted following certain rules, the cell will have either one or zero. It is a calendar sheet so it will have days of the week (both with dates and name).
The sheet cannot be changed format as it is needed for some reporting.
We have to be able to add a column / calculation at the end of the calendar to show "instances" This means if = 1 and previous cell is = 0 then count/sum, if =1 but previous cell is also = 1 then don't count / sum. If cell is = 0 don't count/sum.

Is there any formula I can use for this?