File in Use

I'm mounting an external device over the network with Mountain Duck; the device is recording a livestreamed video. When the video is done, I want it transferred to an external HDD/SSD.
I have the rule down to do this, but I've found that I need to include a condition to wait until a while after the recording is expected to be done (currently 24 hours), otherwise Mountain Duck gets wonky. I'd like to have the process start earlier and it seems that a "file (not) in use" condition would be useful; however, I'm not finding that.
Am I missing this condition — or is Hazel?
I have the rule down to do this, but I've found that I need to include a condition to wait until a while after the recording is expected to be done (currently 24 hours), otherwise Mountain Duck gets wonky. I'd like to have the process start earlier and it seems that a "file (not) in use" condition would be useful; however, I'm not finding that.
Am I missing this condition — or is Hazel?