How to write a bash script based on the modified of the files?

This is using SuSE Linux Enterprise 12.3. We are thinking of writing a bash script to find out the whether a group of files with *.rf were updated for the past 4 hours. We wanted to ensure that at least 1 or more of these *.rf files in /usr6/MAPS4/ folder. We are thinking of checking based on the "Modified date" of the file. If at least 1 *.rf file was updated for the past 4 hours, that means thing is working fine. Else, if none were updated, an alert will be triggered.

How to write this bash script? Please show with example.

Thanks in advance.