Depending on your version of Splunk (given that you're using the newer search element syntax, i suspect you're ok), but one option may be to use changed conditions, to show/hide different panels as described in an unset example in the docs: http://docs.splunk.com/Documentation/Splunk/6.2.0/Viz/PanelreferenceforSimplifiedXML#unset (they're using a drilldown instead of an input changed, but same principle)
Another option may be instead of a search ref, have a search string that uses either the loadjob or savedsearch command instead. Check the docs for syntax, but string substitutions should work there.
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