disable submit when clicked, and when you go back, re-enable it?

[ShadowIce]

How can I make this code disable the submit button once it has been pressed, then if the user hits back or GOES back, it will re-enable it again?

 

<SCRIPT LANGUAGE="JavaScript" TYPE="text/JavaScript">

function formControl(submitted) 
{
   if(submitted=="1") 
    {
   commentForm.Submit.disabled=true
   alert("Thanks for your comments!")
    }
}

</SCRIPT>

 

Thanks!

 

ShadowIce~