onmouseover event

Question

when am using mouseover events in as.net with button control i want to interchange the text of buttons when mouse is over the button

i have two buttons

  

   

yes

                   

no

when the mouse is over button 'no' then the button1 text should interchange as no and button2 as yes 

i used the below code but its not working

        Button2.Attributes.Add("onmouseover", "this.value='yes'");

        Button2.Attributes.Add("onmouseout", "this.value='no'");

        Button2.Attributes.Add("onmouseover", "Button1.value='no'");

        Button2.Attributes.Add("onmouseout", "Button1.value='yes'");

why is it so?