Drop Down Menu linked to COUNTIF Function

We are a doctors office using excel to track outside physician referrals...

I have 13 sheets in my workbook, 1 for each month, and 1 yearly sheet which totals all referrals by month for each of the 2000 referring physician . Each monthly sheet is a report which lists all incoming referrals.

Monthly Sheets:
Column F: Type of referral
Column W: Physician's name.

Yearly Sheet:
G:R Monthly Totals
U: Physicians Name

On the yearly report, referrals are accumulated by:
=COUNTIF('Nov09'!$W$4:$W$1879,$U5)

I would like to have a drop down menu that lists types of referrals like:
X-Ray, CT, New, MRI, ALL

All should count all referrals, but each other selection should separate and only calculate those types of referrals.

I was thinking i need some sort of multiple criteria COUNTIF function linked to a drop down menu... Any help would be greatly appreciate!!!

Thank you