A mechanism in a block diagram environment allows the modeling of an execution behavior of a block in a block diagram, where a user selects the execution behavior from a plurality of functions related to the block diagram and where the execution behavior of the block is performed when at least one model variable associated with the block satisfies a user-specified condition is disclosed. States and other internal data in the designated block are initialized upon the satisfaction of the user-specified condition. The illustrative embodiment of the present invention also allows the internal data to be reset upon the ending of the event, such as the modeled introduction or withdrawal of power. The execution behavior may be suspended and resumed multiple times during the simulation in response to multiple occurrences of the specified event. The present invention also allows for selected data to be exempt from the reset process so that the selected data is nonvolatile.