<script language="JavaScript">function chisRD(){
if (document.forms[0].isRD.checked){
document.forms[0].RDzw.disabled=false;
document.forms[0].RDzw.style.background="#FFFFFF";
}else{
document.forms[0].RDzw.disabled=true;
document.forms[0].RDzw.style.background="#DFDFDF";
}
}</script>
 <form name="htmlform" method="post">
<input type="checkbox" id="isRD" name="isRD" value="Y" onclick="javascript:chisRD()"> 
<input name="RDzw" type="text" id="RDzw" style="background:#DFDFDF" disabled>
</form>