Count rows based on three criteria, including blank cell

[Kees1]

I have three columns, the first two contain a date, the third one a number or a blank cell.
I am trying to count all the rows in those columns where a date (in D3) falls between the dates in the first two columns and the third column contains an empty cell.

At the moment my formula looks like this:

=COUNTIFS(A2:A73,"<="&D3,B2:B73,">="&D3,C2:C73,"")

I have also tried:

=COUNTIFS(A2:A73,"<="&D3,B2:B73,">="&D3,C2:C73,ISBLANK(this.cell())

The first two critera seem to work, but as soon as I add the third one (check for empty cell) the result is always 0.

[mariosv]

I think no option for use a function inside COUNTIFS() function, but it easy to do with SUMPRODUCT():

=SUMPRODUCT(A2:A73<=D3;B2:B73>=D3;ISBLANK(C2:C73))

[Kees1]

Thanks that really helped. It works, though it seems a little unintuitive, I would never have worked out by myself to use this function for what I was trying to do.