Max ditaot publishing executions

Hi,

I'd like to limit the maximum number of publishing instances to 1. In other words, 1 publish at a time, and the rest are queued.

I've tried the following in "Background task XML settings" and recycled the app pools and am not getting what I believe to be the desired effect of queued publishing

<group name="Export" maxExecutions="1">
<handlers>
<!-- <add ref="INBOXEXPORT"/>
<add ref="REPORTEXPORT"/>
<add ref="SEARCHEXPORT"/>
<add ref="PUBLICATIONEXPORT"/> -->
<!-- New publish -->
<add ref="PUBLISH" />
<add ref="PUBLISHDITADELIVERY" />
<!-- Unpublish -->
<add ref="DITADELIVERYUNPUBLISH" />
</handlers>
</group>

Mario