I have a list that is used to track trucks leaving my facility and arriving at another facility. I am currently calculating the travel time for the trucks with a calculated column in the list. Example: Arrival Time - Departure Time = Travel Time. I would like to create a workflow that will calculate the Travel Time without the Arrival Time having to be entered. Example: Now() - Departure Time = Travel Time. I would like for this workflow to update the list item every 5 minutes until the Arrival Time is entered. Can anyone provide an example of how to do this?