Hi Lobna,
Well when you book or prebook an employee to a course, the system checks if the employee is valid for the entire business event/business event type period.
So either the Business Event type exist before the entry date or it exist after the departure date. As explained on the former URL link I attached.
You may use the table T777BIRTH to extend the maintenance of the relationship between a P and another object. In your case you would probably need to use this table to enter the extended maintenance of relationship of a person to a business event type with relationship 27 (prebooked) from birth date of till the highest date (31.12.9999)
Normally, a person can only be booked or prebooked to a business event or business event type if the person is active during the entire period of the business event (type). However, using table T777BIRTH it's possible to extend relationship
maintenance if the period comes before the hiring date (From birth) or after the leaving date (Until highdate). There you can
extend the booking relationship so you can book these employees.
The reason could be the entry-date. You can try to solve this by customizing table T777BIRTH according to your requirement to book these kind of people anyway. P B 025 E X in field BIRTHX allows to create the relationship with a BEGDA before the entry-date.
before doing such change, look first what are the begin and end date of the business event type and the active period of the employee to make sure if you really need to extend the maintenance of the relationship, or you could simple decrease the validity period of the business event type.
Best regards
Hadrien