var submitcount=0; 

function disableSubmit() 
{ 
    if (typeof(Page_ClientValidate)=='function') 
    { 
        if (Page_ClientValidate() == true) 
        { 
            return checkSubmit(); 
        } 
        else 
        { 
            return true; 
        } 
    } 
    else 
    { 
        return checkSubmit(); 
    } 
} 


function checkSubmit() 
{ 
    if (submitcount == 0) 
    { 
        submitcount++; return true; 
    } 
    else 
    { 
        alert('The order has already been submitted.'); return false; 
    } 
}