>Therefore, When I use this class in the form, I just put fstock to the cform, and cvalue = thisform.txtstock.value. But It fail for me to call form (fstock) why? coding will be appreciated. Thanks

What is the error? If your form isn't modal, your private variable may go out of scope part way through your form. You should use the TO clause of DO FORM, and RETURN a value in Unload() of the form.

DO FORM (This.cForm) TO retval

Make sure you are using a form property or somehting instead of a control's value too, because the control will have destroy()ed by the time Unload() fires.