Control file getting access to masterpage control

I was assigned a task to add a checkbox to control to a series of webpages. I created a copy of my current masterpage and for these 6 pages I'm going to use this version. I added the checkbox to the masterpage. When I load my first page it runs

masterpage - Page_Load

control(ascx) Page_Load

After the page loads I check the checkbox and it runs masterpage - Page_Load

control(ascx) Page_Load

masterpage - chkBox_CheckedChanged

I have to know that it was checked in the page_load of the control(ascx) page. How can I get this info before or during the controls page_load?

Thank you