Count rows with multiple null and not null criteria

Hi, hope someone can help with the, have been googling this for a while but no joy.

I am using Excel 2007. I have a table of data and I want to count the rows where column A is not null and where column D is null. So it would like something like this:

=SUMIFS(A1:A1000,IsNotNull,D1:D1000,"")

Except that IsNotNull does not exist.

Thanks.