function
valid(form)
{
var field = form.T1;  
var code = parseInt(field.value);   
if(!code)
{
alert("You must enter a code.");
return false;
}
else if (code != 904)
{  
alert("The code you entered (" + code + ") is not recognized. Please check it and try again."); 
return false;
}
else if (code == 904)
{  
return true;
}
}