Wrapping Tags Around Selected Text In A Text Area!!

I'm trying to 'wrap tags' around text in a text box.

<script language=javascript>
function insertFauxTags(fauxTag, e, endFauxTag)
{
var e = document.frmAddNewForum.txtTopicMessage.selected;
document.frmAddNewForum.txtTopicMessage.Value += fauxTag + e + endFauxTag;
}
</script>

And my form:

<form runat="server" id="frmAddNewForum">
<asp:textbox id="txtTopicMessage" runat="server" cssclass="formtext" rows="5" textmode="MultiLine" width="95%" style="width:95%"></asp:textbox>
</form>

And here's how I'm calling the function:

<a href="javascript:insertFauxTags('[p]' + e + '[/p]')"><img src="http://www.<%=strSiteName%>/images/parabutton.gif" border="0" alt="Paragraph" /></a>
When I run this in FF I get 'e' is not defined - any ideas?