COUNTBLANK in dynamic range

Hi,

I really hope you can help me with this because I'm starting to think it is impossible.

I have two columns if data (in the example columns D & E). One stating various events and the adjacent column stating why people hadn't attended the event.

I need to count the number of people who didn't attend each Event (the blanks) and show this in column M. However I cannot just simply use a COUNTBLANK on a specified range, because this sheet changes daily and there are different numbers on each event daily.

Therefore I need to firstly make it acknowledge which rows have the Relevant event type in (i.e all the rows which state 'Design'), and then count the blanks in the adjacent column. Can anybody help me because the dynamic range is really throwing me and I cannot find a way around this??? I have attached the sheet so you can look at it and hopefully things will make more sense.

The example.xls

Any help will be greatly appreciated, even just to say if it cannot be done.

Millie