In an actual construction operation, a site manager usually has to make real-time decisions on dispatching shared resources to competing activities. To ensure a valid simulation of the operation on a computer, properly modeling how such decisions are made is crucial. This article presents two rules for guiding resource dispatching during simulation, addressed as objective function-based and control variable-based rules. The objective function-based rule defines an objective function for each activity which is competing for the resource; and an activity is selected if it has the optimum (either minimum or maximum) objective function value. A control variable is used to describe an indicator of the status of a simulation. Through structured conditional statements, it is used to control whether an activity shall or shall not be selected to receive a releasing resource according to the updated value of the control variable at the time when the decision is made. The algorithms are implemented in the ABC simulation system. A case study is presented to illustrate the usage and advantage of the presented rules. The results show an improved process production, and more stable and balanced operational behavior of the process after the real-time human decisions are modeled in the simulation. Through the animation function, a user can visualize on the screen that the decisions are dynamically made corresponding to the status of the simulation in the manner similar to what a site manager would make on the site.