Excel 2007 : excel 2007 - want to count pairs of strings between 2 columns

Hi I'm hoping that someone out there can help with a problem I've been having for a few days now. I have an excel spreadsheet that the contains information returned from a survey. I am quite pleased with it, it tallies up the number of yes/no responses to questions and and displays positive and negative responses as a percentage of the total number of people surveyed. However, I have run into a problem with the last thing I want it to do.

I have two columns - the first one (A) headed 'would you like to be contact by phone' and the second (B) 'Would you like to be added to our register" - each columns has a long list of 'yes' and 'no' answers. I want excel to have a cell that calculates how may times 'yes' appears in column A and B - basically counting the number of pairs.

I hope this makes sense and that someone out there can help. Any help given will be much appreciated.