formulas for drop down menus
 

I am having great difficulty trying to figure out how to use a formual with a
drop down menu. My situation is as follows. I have a vacation planner that
I have created validated drop down menus for and now I am trying to find a
formula that will calculate the count result when an item is selected from
the drop down menu. Here is what my drop down menu looks like and the
formula I have been using

Drop Down Menu Contents
P
P*
0.5P
0.5P*

Formula:
=COUNTIF(B5:U5,"P")+(COUNTIF(B5:U5,"0.5P")/2)

If I do not use that drop down menu the formula works fine. Please HELP!