Field help (BPC5MAIREP) 

This field takes the first sales representative code specified in the prospect/customer record.

If a sales representative code is defined, this field is inaccessible to the user.

If no sales representative code is defined, it is not possible to define secondary sales representatives. The main representative must be declared in the prospect/customer record before the start of the definition of secondary sales representatives.

In this case, the field is accessible to the user. The entered code will be transferred to the prospect/customer record.