You can use a Statistics Collector to measure the duration of each unload action. In the attached model the collector reacts to tokens entering and exiting the "Unload Item" activity. In the entry event a new row with the token as 'row value' is created. The exit event 'finishes' the row, so that the next time the token is used as row value a new row is created again. In the Triggers tab the current model time is written to a label belonging to the row. When the token exits, this value is used to get the duration.
A Calculated Table sums up the duratians per destination object and divides that value by the total model time to calculate the overall utilization.
https://help.autodesk.com/view/FLEXSIMIN/2027/ENU/?guid=FlexSim_User_Manual_gettingdata_advanceddata...
https://help.autodesk.com/view/FLEXSIMIN/2027/ENU/?guid=FlexSim_User_Manual_gettingdata_advanceddata...
Edit: Alternatively and somewhat simpler: Set the state of the queue to some state representing the unload action and use a default state chart. Adjust the state names and which states count as utilized in the State Table that is linked to the chart.
