Access datatemplete header checkbox in codebehind

Question

hi gyes,
            
             i added checkbox dataTemplate in DataGridTemplateColumn.HeaderTemplate using XML code for check/uncheck 

             All checkboxes in datagrid column in WPF Application.
                          my requirement is when i uncheck all checkboxes in datagrid column then datatemplate checkbox is also uncheck For that need to Access that              datatemplate checkbox in codebehind  how plz help.
             thanks.