I have a grid class (modify from TASTRADE) that calculates Sum of a column but it gives me GPF. If I take out the 'CALCULATE' statement, everything works fine. Is this a Microsoft bug or not?

My CalExpr is: SUM(carddet_vw.qty*carddet_vw.price)


LOCAL i,lnOldArea, ;
lnOldRecNo, ;
luKey, ;
lcOrder,;
lnResult,;
lcExpression

lnResult = 0.00
IF EMPTY(THIS.CalExpr)
return lnResult
ELSE
IF EMPTY(this.RecordSource)
RETURN lnResult
ENDIF

lcExpression= " " + THIS.CalExpr + " "
lnOldArea = SELECT()
SELECT (this.RecordSource)
lnOldRecNo = IIF(EOF(), 0, RECNO())
lcOrder = ORDER()
luKey = IIF(!EMPTY(lcOrder), EVAL(lcOrder), "")

IF !EMPTY(lcOrder) AND SEEK(luKey)
calculate &lcExpression;
WHILE luKey = EVAL(lcOrder) ;
TO lnResult
ELSE
CALCULATE &lcExpression;
TO lnResult
ENDIF

IF lnOldRecNo <> 0
GO lnOldRecNo
ENDIF
SELECT (lnOldArea)
ENDIF

return lnResult