Counting Blank cells in a range

[Jackie11]

What forumla would I use to count blank cells in a range?

For example.

A B C
1 1231 - 001 Bill 1/08/2013
2 1232 - 001 Bob
3 1233 - 001 Billy 17/2013
4 1234 - 001 Brad
5
6




How can I count the blank cells in Column C, only if there is data in Column A. Therefore the answer should be '2' because it will exclude row 5 and 6, as there is no data in column A in those rows.

Thanks for the help!