amount for working hours of volunteer on an event
Without CiviVolunteer, you can add a numeric custom field for participants and call it volunteer hours.  When you register the participant for the event, or by editing it later, you can record those hours in the field.

You will still need to have a way to total up the hours if you want to say something like, "Dave volunteered 20 hours at events this year."  You'll need to build a custom report or at the very least export participants and sum the values in a spreadsheet.

CiviVolunteer was really envisioned with your sort of situation in mind, so you might consider downloading it.