Agenda - Time duration column

Hi all,
Cannot find any info on this, if someone has a solution for this that has slipped past me, please do fill me in Trying to get the 'duration' of an assignment to automatically print without manually adding it myself. Is there something I'm missing? Thank you in advance

Christine
Rouse Hill TM
Club number: 04175602

Duration of a role is the difference between start time and end times of the roles that is shown on the left of the agenda role.