Why do I get the error message, "sum.prg does not exist"? This didn't happen in rpeviopus version s of VFP, but I do understand that some SQL code has been tightened up. So, what do I use if not SUM()?

SELECT ;
		APTRXFIL.VOUCHER_NO, ;
		APTRXFIL.INV_AMT, ;
		SUM(APTRXDST.DST_AMT) AS DST_AMT ;
	FROM ;
		APTRXFIL, ;
		APTRXDST ;
	WHERE ;
		APTRXFIL.VOUCHER_NO = APTRXDST.VOUCHER_NO AND;
		APTRXFIL.INV_AMT <> SUM(APTRXDST.DST_AMT) ;
	GROUP BY ;
		APTRXFIL.VOUCHER_NO, ;
		APTRXFIL.INV_AMT ;
	INTO CURSOR tmpAPTransactions