regarding the user exit USEREXIT_MOVE_FIELD_TO_KOMK...

hi i am working on sales order user exit. my project is upgradation project. already some code copied from 4.6 to ecc 6.0 version for MV45AFZ4.in MV45AFZ4 the user exit is USEREXIT_MOVE_FIELD_TO_KOMK. what is the importance of this user exit????. i want to know the functionality..