Unable to calculate highlighted cells.

Can anyone help and excel idiot???

Please if you are able and willing to shine a light then do so in easy speak haha no technical blurb as I am not too clever with excel only know the basic when it comes to spread sheet design.
My problem is that I have recently designed a spread sheet with the full 2012 year on it. On this calendar is my shift pattern for each individual month. Every shift involves two travel days (there and back) so on the spread sheet I have highlighted my shift pattern in grey and the each time I have a travel day that cell is coloured green. Is it possible to somehow have the excel mega brain calculate only cells highlighted green and then another calc to count grey cells? Make sense????
I know how to do calculations within the cell by doing = and then the cells I want to calculate but never highlighted cells only!
Please help,
Also I'm on 2010 MS Office

Cheers