Restrict javascript usage in RTE

I use the RTE in an event calendar using ASP where a user can add and edit events. I don't want users adding malicious code to the system so am trying to limit the use of javascript. Having a strange problem though. When a user types the following in the RTE text area (not HTML view):
<script type="text/javascript">alert("I am an alert box!");</script>
it is converted by the RTE to:
&lt;script type="text/javascript"&gt;alert("I am an alert box!");&lt;/script&gt;
when entered in the data base.

Should a user choose to edit this entry, they use another page where the previously entered values in the database are used to populate the form elements, the RTE text area included. So for example, the text area uses code like this:
<textarea cols="65" rows="33" name="exampleEventDescription" id="exampleEventDescription"><%=(exampleRS.Fields.Item("exampleEventDescription").Value)%></textarea>

when I do this though, the text area entry gets converted back to:
<script type="text/javascript">alert("I am an alert box!");</script>
and the alert box pops up.

I can't figure out how to stop this from happening. Any help?

Cheers, that really helped. I did have to modify the syntax just a bit to get it to work, but saved me from pulling all my hair out.

<textarea cols="65" rows="33" name="exampleEventDescription" id="exampleEventDescription"><% = Server.HTMLEncode((exampleRS.Fields.Item("exampleEventDescription").Value)) %></textarea>