Hi One way you can retrive it by this way
First in your master page code behind try to create a property that exposes this control you are going to access.
public String LabelValue
{
get { return lblinMaster.Text; }
}
Then in your content page (ASPX) add a reference to master.
<%@ MasterType VirtualPath="~/MasterPage.master" %>
You are done and you can access
Master.LabelValue
in content page code behind.
Ofcourse if you are trying to control everything, try to create a base page and keep the fields you want to control here, inherit all your pages from it.
Thanks,
Debata