Excel 2007 : Tracking dates, except for the year old ones...

i have an excel spread sheet that track business trips of the members of our company. the tracker has all the trips each member has taken in their carreer, but all we track are the dates from the last year from the current date. it uses two side by side cells to display the dates they left, and the dates they returned. then it subtracts the return date from the left date and gives me the number of days for that trip. multiple trips are stacked verically. then the number of days away for each member is then totaled.

what i am looking for is a formula or a condition that tells me if the dates in both fields are more than one year old and if so not calculate them into the total cell which just adds them all up at the bottom.

any ideas??