Naomi,

I'ld be worried that a select might change the active alias so I'ld use code like below. But the reason is probably in a different interpretation in SQL and xBase (as modified by SET ANSI and set Exact <g>) of
inv_no+salesman = m.ccinv + m.Slsman

>

SELECT Comision
lnRecno = RECNO()  && Dunno what for

SELECT SUM(rate*SHARE/10000) AS crate 
                WHERE inv_no+salesman = m.ccinv + m.Slsman ;
              	FROM comision INTO ARRAY laArr

SELECT Comision
SET ORDER TO com_inv IN comision
IF SEEK(m.ccinv + m.Slsman)                	
	SUM (rate*SHARE/10000) TO cRate WHILE inv_no+salesman = m.ccinv + m.Slsman
ELSE
	cRate = 0
endif		
                	
lcRate = EVL(laArr[1],0)
IF NOT m.cRate = m.lcRate
 	=MESSAGEBOX("Found a mismatch on " + m.ccinv + m.Slsman)
	_cliptext = _cliptext + "Found a mismatch on " + m.ccinv + m.Slsman + " cRate = " + ;
        	TRANSFORM(m.cRate)  + " laArr[1]= " + TRANSFORM(m.lcRate)
ENDIF

regards

thomas