If you are using the 400 Indexer, you can specify the field such that it is only located once in the first document of the report and the same value used in every document. For example,
FIELD6=0,87,9,(TRIGGER=3,BASE=0,DEFAULT=X'6D5CC6C9D5C4D6D5C3C55C6D') /* _*FINDONCE*_ */
INDEX6=X'C481A385',FIELD6,(TYPE=GROUP,BREAK=NO) /* Date */