Is this possible? I have a structure like this:

A B
-------------------
5/10
5/10 6/10
5/12 5/25
5/15
5/16 5/30

I'd like to count the number of entries in column A only if the
adjacent cell in column B is blank. So, in the example above, I'd want
to see a count of 2 as the answer.

Can I use the COUNTIF for this, maybe with OFFSET? Or do I need to do
a database function? Seems like it ought to be easy, but I'm missing
something...

Thanks for any help!