We need to write a function, usable in the XML dial plan, that tests the inbound CID (not destination_number) against a &quot;white list.&quot;  Something on the line of,,,  <br><br>&lt;condition field=&quot;ISWHITE(${caller_id_number})&quot; expression=&quot;true&quot; &gt;<br>

<br>Question:  In such a use case, must ISWHITE() be a custom application/mod written in C, per skel.c, or can it be a script written in lua or p-language or the like?<br><br>It&#39;s clear from wiki and docs we&#39;ve seen that &lt;action ... /&gt; can have lua or p-language scripts; but it is not clear about the &lt;condition ... /&gt; clauses and where to locate and &quot;hook&quot; them in.<br>

<br>Guidance and any pointers to docs/examples greatly appreciated.<br><br>With thanks,<br>/S<br>