Have you considered using a "Data Recorder" atom from the group "Results"?
Here you can create a variable to log on the tab variables. I would use option nr. 4: "LeadTime from label" and define on the point where the product is passing first a label on the product ( Label([LabelTime], i) := Time ) containing the passing time (either on the On Entry - or On Exit Trigger).
Then at the Data Recorder, the difference between the time the product has passed the conveyor (defined on the label) and the current time at the Data recorder is logged.
Perhaps you have to make small adjustments to log exactly what you want, but I hope this is helping you.