In a discrete event model, you can control the order that time ties (two or more events occurring at the same time) are processed. ExtendSim will put the blocks on the event calendar in simulation order. Blocks with a lower simulation order will receive their event message first. You can change the simulation order with the following steps:

Go to Run > Simulation Setup > Continuous tab. Under Simulation Order, choose Custom (Advanced only)

Under the Model menu, turn on Show Simulation Order.

Select an event scheduling block. Choose Set Simulation Order from the Model menu. Set your Custom Simulation Order.

Note, the simulation order will only make a difference if two or more events occur at exactly the same time. If the events are not exactly at the same time, events will occur in chronological order.