<div onKeyUp="chklen()">     
$_MESSAGE$     
</div>

<script language="JavaScript" type="text/javascript">     
function chklen()     
{     
max_limit=20000;     

str = document.addform.message.value;     
len = str.length;     

if (len > max_limit)     
{     
str = str.substring(0,max_limit);     
len = str.length;     
document.addform.message.value = str;     
}     

document.addform.fcounter.value = (max_limit - document.addform.message.value.length);     

while ( document.addform.fcounter.value<0)     
{     
document.addform.message.value = str.substring(0,len-1);     
str = document.addform.message.value;     
len = str.length;     
document.addform.fcounter.value = (max_limit - document.addform.message.value.length);     
}     
}     
</script>