When setting the value of a System Variable in a Panel without changing the value, the CAPL event procedure OnSysvar_Update is not called. Only value changes of System Variables in Panels will call a CAPL event: with every value change OnSysvar and OnSysvar_Update are called.
When using the predefined Symbol Panel, the sending of a System Variable with the same value again can be forced. The predefined Symbol Panel can be accessed via the Symbol Explorer:
The CAPL event OnSysvar_Update is called when the same value for a System Variable is sent again in the Symbol Panel (it is also called when a changed value for a System Variable is sent). The CAPL event OnSysvar is called only when a changed value for a System Variable is sent.