Event-handler procedure

Event-handler procedures were introduced in Excel 97 they can be used in Excel 97 or Excel 2000. Event-handler procedures provide more versatility than the automatic procedures provided with Excel 5/95. 

Event-handler procedures are not written in the usual VBA modules, but in the code modules associated with a worksheet or workbook. For example, to install a new menu command when a particular workbook is opened, put the event-handler procedure in the code window for ThisWorkbook (use the Project Explorer to locate the node for ThisWorkbook, then click on it to display the Code window). 

Figure 18.3. An event-handler procedure to install a custom menu command.

Another major hazard in high-integrity systems, tasks terminating silently, has been addressed in Ada 2005 with a new mechanism for setting user-defined handlers which are executed when tasks are about to terminate. These procedures are invoked when tasks are about to terminate (either normally, as a result of an unhandled exception, or due to abort), allowing controlled responses at run time and also logging these events for post-mortem analysis. 

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