How to divide current year value by previous year value

Dear power BI community, I would really appreciate If you could help me out with the following issue

I have a table which contains the following variable.

Company       Year    Quarter     value 1  value 2 

Company 1     2010    Q1            123         123

Company 1     2010    Q2            123         123

Company 1     2010    Q3            123         123

Company 1     2010    Q4            123         123

Company 1     2011    Q1            123         123

.

.

so on 

Now I want to create a new column (using custom column) with formula:

                        = current year/ previous year

i.e. for 2011 Q1 it will be:

                        = (2011 Q1 value1)/ (2010 Q1 value1)

Any ideas, how to do this on M language?

Any help will be much appreciated.

Thanks