What I'm trying to do is count how many invoice numbers starting with 6 where
completed by a certain date. I've got a column with the date it was
completed and a column of invoice numbers.

Here's what I have so far:
for the date =COUNTIF(H6:H1000,"<"&AB1)
for the invoice numbers =COUNTIF(C6:C1000,"6*")

I just can't get it where it counts them if the row matchs both.

I'm useing Excel 2003 and I'm not allowed to upgrade it, otherwise I would
use the COUNTIFS function in Excel 2007.