How to change the text of a button in side a Gridview of ASP.NET

How to change the text of a button in side a Gridview of ASP.NET

I have a button inside a grid view. The button is in the <HeaderTemplate>
of a grid view. The button text is Select All.
Condition:
When I checked the button Select All then all the check box below to this
are checked (In side the grid view).
At that moment the button text should change to Unselected All & the check
box are also unchecked inside the grid view.(Like we shown in the Yahoo
Mail or )