MathCad Add-In for Excel: can not save result?

Hi,all

I create a mathcad object and use variable in0 to receive data from excel. I wirte a assignment statement in the document, ret:=in0. I save the object into a .xmcd file and reopen it using mathcad, ret is always 0 no matter what in0 is before saving. Does it mean that the calculation result can not be saved? Is it possible to save the result through mathcad automation interface?

Thanks