Printing Customer Product Code

Experts,

lost (or blind) at the moment.

Want to print the customer product number (field name CUSTOMER_PRODUCT in PRDO) on the delivery note printout.

Have checked the "standard" variable in smartform ( IS_DLV_NOTE ), but can't find the customer product here.

Also checked tables (/SCDL/DB_PROCI_O, /SCDL/DB_REFDOC), can't find it here.

Am I blind? Could someone pls give me a hint?

Thanks

Michael