How can I put the field in the "SUBHEAD" without sorting that field with "BY" ?

ON TABLE SUBHEAD
"test"

Do you want it printed as a result of another BY field break? Kamesh's example will print the subhead on the first page.

Here is a 'silly' example:
TABLE FILE CAR
PRINT DEALER_COST RETAIL_COST
BY COUNTRY
ON COUNTRY SUMMARIZE DEALER_COST
ON COUNTRY SUBHEAD
"{COUNTRY FIRST MODEL {FST.MODEL"
ON COUNTRY SUBFOOT
"{COUNTRY LAST MODEL {LST.MODEL "
END
"{" represents the less than symbol