specifying a specific tab when executing code in an add-on

I am creating an add-on that has an issue of focus.  If I have
multiple tabs running in parallel that all trigger the add-on
simultaneously on load, all the code will be executed against the tab
that has focus.

Using the following to listen for the page load:

gBrowser.addEventListener("DOMContentLoaded", function(aEvent)
{always(aEvent);}, false);

So, the issue is that the code is being triggered on a tab load, but
isn't executing in the calling tab, just the tab with focus.  How can
I specify a particular tab of unknown index to execute the code in,
regardless if that tab has focus or not?