Solution : https://service.sap.com/sap/support/notes/531327 (SAP Service marketplace login required)
Key words :
import parameter reference field/structure if_vbeln likp-vbeln if_posnr lips-posnr save, typing reference type if_vbeln, likp-vbeln if_posnr, lips-posnr, terms apo shipment scheduling, user exit 'exit_saplv03c_apoint_001', user exit exit_saplv03c_apoint_001reason, source code corrections, function module 'exit_saplv03c_apoint_001', field catalog