For example, you might have a reactor that's responding to an entity being added to the drawing. In the reactor a global variable is tested to see if the process has already been activated. Of course, for speed of operation I recommend using integers or Boolean values instead of the string names just mentioned. The key in all cases is to understand how reactors happen. Once you understand this concept, it's relatively easy to keep reactors from causing too much interference in normal operations.
Experimentation is the key.
The process is easy. Using the Object pulldown option, select the AcadDocument option, as shown in Figure 1. The Procedure pulldown option will now contain all the various reactors you can program. Figure 2 shows a portion of this drop-down list. To program one of the options, select it in the dropdown list and the procedure will start automatically.