I am trying to specify a relative time range for a specific field in my search rather than the "_time" field (i.e finding the last 36 hour results on a field called "LogOut"). I cannot just do this "on _time" as I need to create a transaction on some fields, and when searched on _time, it brings results I do not want to see as I have keepevicted results on.
What you need to do is determine the "start time" and "end time" values to compare them to your field for time. That can be done in various ways depending on how you're calculating.
I've done this in a dashboard comparing against a field called "activity_time" and using the earliest and latest time from the timepicker (token name TimeRange). This is how I did it but there may be a better/easier way.