Write as follows in order to kill divide by zero error. D=SQR(POW(X2-X,2)+POW(Y2-Y,2)) IF D>0 THEN X2=X2+(X2-X)/D:Y2=Y2-(Y2-Y)/D The following code is another solution. D=SQR(POW(X2-X,2)+POW(Y2-Y,2)) IF D>0 THEN A=ATAN(Y-Y2,X-X2) X2=X2+COS(A):Y2=Y2+SIN(A) ENDIF