The ASSOC.WITH keyword is a field qualifier to specify that the field is to be associated with some other named field.
field.name ASSOC.WITH name
The ASSOC.WITH keyword causes field.name to be treated as associated with field name.
LIST ORDERS PART.NO QTY EVAL "SELL * QTY" ASSOC.WITH PART.NO
This command processes records from the ORDERS file and reports the multivalued part numbers, quantities and calculated line total value for each record. The evaluated expression is treated as associated with PART.NO.