I have 2 columns which are designed to show whether a machine is switched on or off during a particular week during the year.

Column 1 is Week: 1, 2, 3, 4, 5, ...52
Column 2 is Value: On, On, On, On, Off, Off, Off, Off, On, On, On, On , Off, Off, Off, Off...

I want to have a cell to count how many times the machine is switched on every year, i.e. if it is on for 4 weeks and then off for 4 weeks, that would count as 1 time of being switched on. If it is on for one week and then switched off, that would also be swtiched on only once. Any ideas?