hi, i'm a newbie in javascript..
recently, i'm trying to do some form validation in javascript...
however, there are some difficulties in radio buttons.

<script type="text/javascript">
function validate()

	if(document.getElementById('interest').value == "2")
		alert("not ok")
	if(document.getElementById('interest').value == "1")


<input type="radio" id="interest" name="interest" value="1">Reading
<input type="radio" id="interest" name="interest" value="2">Sport

<select name="sport" id="sport">
<option value=""></option>
<option value="1">Swimming</option>
<option value="2">Gym</option>


<input type="submit" value="submit" onclick="validate()">
I wish to make, if user selected Sport at the radio button, then he will need to make a selection at the Sport field. Else, if the user selected Reading at the radio button, the select Sport field is disable...

how can i make it works?

thank you!