Conditional Formula help

Hi all,

Some help here would be very much appreciated! I'm sure it's really simple but cannot figure it out.

I have a table of percentages, and need a column that will return either "yes" or "no" depending on several conditions.

Please see below example

excel.JPG

At the moment I manually have to go through fields and insert 'Yes' in email required, if the previous two months are below 80%, and an email has not already been sent.

So in summary I need a formula that returns Yes, if the most previous two months are below 80% and an email has not already bee sent.

Thanks in advance!