To run a macro when the BeforeInsert or AfterInsert event occurs, set the BeforeInsert or AfterInsert property to the name of the macro.
You can use these macros to display messages or useful information. For example, you can have the BeforeInsert macro display data the user needs when entering a new record.
You can use the CancelEvent action in a BeforeInsert macro to cancel the creation of the new record. When you use the CancelEvent action in a BeforeInsert macro, the focus returns to the new record, which is blank (the character that the user typed is deleted).
You can’t use the CancelEvent action in an AfterInsert macro.
BeforeInsert, After Insert Events — Event Procedures.