Changing the button text at run time....

hi frinds I have a issue here..

I need to change the Button text when I clikc the button as well as it should disable ( that user dont have access to double click on that)

ex : I have buttong text like Submit.. when user click submit button I need to change that submit text to some thing like Processing...

so that user knows that its processing..

ASAP

thanks
...