Yes Rick. I got the slowness in Excel 2007 too (I do not have 2003). I think it is because of 1/1/9999. When I changed the formula to,

=COUPNCD(A1,"1/1/"&YEAR(A1)+1,4,1)-1

and tested with 10000 cells, calculation was normal. Also, I didn't know it is a part of Analysis ToolPak in earlier versions.