Update Global Variables
Ok figured it out. I was going about it completely the wrong way. As the field in question is an Entry type, I needed to use the Relations Service

$globalSet = craft()-&gt;globals-&gt;getSetByHandle('[globalSetHAndle]');
$selectedField = craft()-&gt;fields-&gt;getFieldByHandle('[fieldHandle]');
craft()-&gt;relations-&gt;saveRelations($selectedField, $globalSet, array($entryId));


Passing null instead of array($entryId) will clear the relation values