Can i count the number of months in a specific range

Hi Everyone..

Refer to the attached excel file,
The green line is the total sum of man-hours that Robin needed to do in a month.
If you look at the data, there are certain month where he does not require to work..

So the data that i want to count is the "Plan Duration" and "Actual Duration"..
Where,
Plan Duration: The month count of when he start to finish (sept 2011 - oct 2012; Count: 14)
Actual Duration: The month count of his actual work.. (Sept,dec,mar-oct; Count: 10)


For Actual duration it's easy for me as I've used
=COUNTIF(F87:AY87,">0")

But I'm Stuck as to how i am going to count my Plan Duration..
Is there a way where i can tell excel to lookup the First value and last value and count the months in between?

I've tried combining index & match but i guess I'm not that great to fully apply it properly..
I know it sounds complicated, but I'll really appreciate it.. Thanks in adv...