Calculating and formatting business days

I don't know if this is in the right area so I apologize in advance if it isn't. Our department is trying to enforce a policy where workers must return all voicemails within 5 business days.

We created seperate workbooks for each of the workers to keep a log of their voicemails. Each workbook has 12 worksheets (Jan-Dec). In each worksheet, Column B lists the date of the voicemail and column O lists the date the call was returned.



I then have a call summary workbook that totals each workers calls and shows me the date of the oldest call that has not been returned for each worker. (below) I use =MIN(IF(O4:O500="",IF(B4:B500<>"",B4:B500))) to give me the date of the oldest call not returned.


summary.JPG


My question is...

1.Is there a way to automatically highlight (or apply some conditional format to) dates in Column B that are older than 5 business days --where there is NOT a date in column O.

2.Can I calculate how many business days between the date in column B and the date in column O?

Thank you