You could do something like this:
<body>
<textarea id="txtArea" onkeypress="onTestChange();"></textarea>
<script>
function onTestChange() {
var key = window.event.keyCode;
// If the user has pressed enter
if (key === 13) {
document.getElementById("txtArea").value = document.getElementById("txtArea").value + "\n*";
return false;
}
else {
return true;
}
}
</script>
</body>
Although the new line character feed from pressing enter will still be there, but its a start to getting what you want.