Compare columns of dates

Hi

I have a spreadsheet with two columns of dates running to 320 rows, which I need to compare row by row and provide given output in and adjacent cell. I aready have the following formula working

=IF(ISBLANK($N$26:$N$320), " ",IF(ISBLANK($O$26:$O$320), "No", IF($O$26:$O$320="N/A", "N/A",IF($O$26:$O$320<=$N$26:$N$320,"Yes", IF($O$26:$O$320>$N$26:$N$320, "Overdue Closed","No")))))

Giving the output- No, Yes, or Overdue Closed, dependant on the test result. I need to modifiy the above formula to add the output Overdue open.

Overdue Open - would compare todays date against the target date in column N. If the target date is less than todays date and column O is blank the output will be Overdue Open.

Thanks