Looking for modification of standard to regenerate SM30 without losing code of custom events

I have table maintenance dialogs generated for custom tables (to use with SM30/SM31), with some custom code implemented by events (no other change). If the generated dialog is deleted and recreated, the links between events and custom subroutines, and the custom subroutines themselves, are deleted. Is there a way to keep the code and the events by changing the standard generation?