I have the following:

Referral received Appointment sent
3/8/09 31/8/09
4/8/09 2/9/09
5/8/09
2/9/09
3/9/09 4/9/09
5/9/09

I would like to count the number of appointments that were sent for
referrals received in each month, e.g. for August it would be 2 and for
September 1.

Is that possible?