Disable buttons on a web page.

Question

Hai,

 I have a web application with two buttons i need to disable one button when the other is clicked. I have put the code btn1.Disabled = true when btn2 is clicked (on server click).
Similarly i put btn2.Disabled=true when btn1 is clicked(on server click). But this is not working . I have a function call in the onclick of these buttons and the buttons are shown disabled after the function is executed. Whereas i want the other button to be disabled before the function call.

Thanks in advance,
It would be great if someone helps me as i need to deliver the product in a day.

Ramu medida