how to access gridview on a user control and save its values

i have a master page, aspx page and a user control.
on the aspx page i am dynamically loading usercontrol multiple times,
this depends on some value in Database,
user control contains a gridview with check boxes,
users select some check boxes and hit save button on the aspx page which is (save button) in the masterpage,
what i want to do is save the selected checkbox value on gridview in the database,
problem is i cannot access the gridview on the aspx page,
i am loading the user control on page init of apsx page.
i am loading user control and adding it on placeholder on contentplaceholder.
i am kind of new to this senario as you must have guessed so any help would be greatly appreciated.
using .net 2.0 in c#
following is the page_init code
base.Page_Load(sender, e);
while (dr.Read())
{
 UserControl uc = LoadControl("UserControl1.ascx") as UserControl;
 ((UserControl ...