Return of Control from a Child form

hi,
I have an application with a MainForm(Parent) and SubForm(Child).
on click of a button the Child form is created. Iam not sure where in
the MainForm,the control is returned when i close the child form.

I need to know this to populate some values in a list box in the
Main form, which were got from the Child form. Is there any other way
to access a control in the Main form from the Child form.

Thanks
sendhil