Determining If Occurrences Exist Within Past 30 Days

Hey all. New guy here with a question I hope I can explain.

I have a worksheet where I need to do what I think is a complex calculation as outlined below. What I need is a formula in the cells of column L that will do the following:

Check the date entered in Column E of the new record determine if the agent entered in column B has any other occurrences of the error description entered in column K within the 30 days prior to the date entered in column E


I thought I was fairly handy with basic formulas, but this may not be the case, and it may not be anything I can achieve with a formula. My goal is to identify repeat offenders within a 30 day window if possible and provide feedback to their managers.

Hopefully I made clear my intent.

Thanks in advance.
Nick