offset_running_time
Description:
Adjust the values in this so that offset is applied to all future running-time calculations.
Parameters:
| this | 
           a Segment structure.  | 
      
| format | 
           the format of the segment.  | 
      
| offset | 
           the offset to apply in the segment  | 
      
Returns:
| 
           true if the segment could be updated successfully. If false is 
            returned,   |