anybody know if you can do a formula that will increase by 1 every 2 hours??

Column A (Open Time) = 13:00 (1 PM)
Column B (Close Time) = 22:00 (9 PM)
Column C (Total) = 9:00 (9 Hours)
Column D (Opportunities) = 4 (could've contacted cst 4 times in 9 hours, 1
opportunity every 2 hours)

so, I need to add 1 per every 2 hours a file was opened. In this case Column
D would give me a value of "4" .

Thanks,
Mayte