Automatic date selection in Excel 2007, VBA?

Hi,

I would like Excel to automatically record which period each record belongs to instead of having users use a manual dropdown, but I'm not even sure if this is worth spending the time on.

please see the attached.

So Col B is where it should say reporting period for each row. I would like Excel to choose the right reporting period based on the date of arrival.

In col K,L, and M, each period has a pair of start date and end date combination. So basically, the logic here is ......if the date of arrival (col c value) falls under....say for example 7/1/2011 and 7/31/2011, then I want Excel to give that row a P 1 under col B automatically, etc.

Data collection will be on-going, so I don't want to have users drag the cell down as they enter new records, which can be cumbersome?

Is this possible? am I making sense?

Thank you