<script language="JavaScript">
<!--
function showValue(obj){
document.all.txtTwo.value=obj.value+twoVal;
document.all.txtThree.value=obj.value+threeVal;
}
var twoVal="";
var threeVal="";
function init(){
twoVal=document.all.txtTwo.value;
threeVal=document.all.txtThree.value;
}
//-->
</script>
<body onload="init();">
<input type="text" id="txtOne" onkeyup="showValue(this)">
<input type="text" id="txtTwo" value="aaa">
<input type="text" id="txtThree" value="bbb"></body>