Does anyone use Foreign function?

["Greg Q. Liu" <liugq@xxxx>]

I have following codes:
 
x=Foreign("^gspc","C",fixup=1);y=(x/Ref(x,-1) - 
1)*100;z=MA(y,40);Plot(z, "",1,1);
 
My result is ko(or other symble)=-100000...00.00, 
does anyone have some different experience?