Hi-
Thank you very much for your reply. The code you gave seems to be what I'm looking for but I don't know where to put it. My XSP is below.
Where do I put the code so that the dojofxWipeIn is called only if "Yes" is selected in the combobox?
Show field below? 
<xp:comboBox id="comboBox1">
<xp:selectItem itemLabel=""></xp:selectItem>
<xp:selectItem itemLabel="Yes"></xp:selectItem>
<xp:selectItem itemLabel="No"></xp:selectItem>
<xp:eventHandler event="onchange" submit="false">
<xp:this.script>
<xe:dojofxWipeIn node="Lewiston"></xe:dojofxWipeIn>
</xp:this.script>
</xp:eventHandler>
</xp:comboBox>
<xp:br></xp:br>
<xp:panel
id="Lewiston"
style="display: none;"
>
Hello World!
</xp:panel>