How to check all the row of the datagrid

Hi,
    I am populating data  in datagridview control once the form loads. The first column of  every row of the datagridview control is having one check box.
                                              One checkbox i have used outside of the datagridview. What i want is if i check the outside checkbox, all the rows of the datagridview control having checkbox should have checked. Plz Help me Out..

Thank U in advance.