SETSELECTIONFILTER on from 143 not working!

On form 143 this simple code that I use all the time is not working ](*,)


GTotalAmount:=0;
GQty:=0;

CurrForm.SETSELECTIONFILTER(LRec1);
IF LRec1.FINDSET THEN
REPEAT
//LRec1.CALCFIELDS("Amount Including VAT");
//GTotalAmount:=GTotalAmount+"Amount Including VAT";
GQty:=GQty+1;
UNTIL NEXT=0;