Determine if video file is still being recorded

I have a folder set up as a video capture folder. The video file is created as soon as the record button is clicked. While recording, the modified date is constantly being updated to the current time. Once recording stops, the modified date stops moving up.
Is there any way to create a rule that would only apply to files where the date modified hasn't changed in awhile? If there was a way to compare the creation time to the current time, that would solve everything, but I don't see anything for that. I think I can see a way to do it if there was a BUT NOT way to join rules (ie run if conditions 1 and 2 are met but not if condition 3 is met), but to be honest my brain is a little scrambled from trying to work it all out.
Any suggestions are wildly appreciated.
Is there any way to create a rule that would only apply to files where the date modified hasn't changed in awhile? If there was a way to compare the creation time to the current time, that would solve everything, but I don't see anything for that. I think I can see a way to do it if there was a BUT NOT way to join rules (ie run if conditions 1 and 2 are met but not if condition 3 is met), but to be honest my brain is a little scrambled from trying to work it all out.
Any suggestions are wildly appreciated.