CRM 2013 - FetchXML & the subgrid

Hi everyone,

I need some help with my code as the implementation of applying custom FetchXml to a subgrid has appeared to have changed in CRM 2011 to CRM 2013.  Please note this is NOT the issue of setParameter vs SetParameter casing as I keep finding all over the net.  My issue is how to reference the subgrid and call the SetParameter method at all.

Here is my code:

function uc_addCaseFilterToCaseGrid() {
   var contactGuid = Xrm.Page.data.entity.getId();

  //create a filter xml
   if (contactGuid != null)
   {
          var filter = "<fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='false'>";
                filter += "<entity name='uc_crecord'>";
                filter += "<attribute name='uc_casemanager' />";
                filter += "<attribute name='uc_cindividual' />";
                filter += "<attribute name='uc_rindividual'/>";
	        filter += "<filter type='or'>" +"<filter type='or'>" +"<condition attribute='uc_casemanager' operator='eq' value='" + contactGuid + "'/>" +"<condition attribute='uc_cindividual' operator='eq' value='" + contactGuid + "'/>" +"<condition attribute='uc_rindividual' operator='eq' value='" + contactGuid + "'/>" +"</filter>" +"</filter>" +"</entity>" +"</fetch>";

	    //add filter
            //var caseGrid = Xrm.Page.getControl("gPR");//var caseGrid = Xrm.Page.ui.controls.get("gPR");
           var caseGrid = document.getElementById("gPR").control;

            if (caseGrid == null)
            {
               //The caseGrid hasn't loaded, wait 1 second and then try again
               setTimeout(uc_addCaseFilterToCaseGrid, 3000);
               return;
            }

            caseGrid.control.SetParameter("fetchXML",filter);
            caseGrid.control.Refresh();
    }
}

This code does not work because the bold, italisized line is causing me a problem.  

If I use getElementByID (not recommended, and not the approach I'd like to take) the code SetParameter executes as expected. 

However, I want to use the following to set the variable:

var caseGrid = Xrm.Page.getControl("gPR");

as I want to ensure future support.  But when I call SetParameter I get an error "Object doesn't support property or method 'SetParameter'". What gives?

I've tried the following:

caseGrid.control.SetParameter("fetchXML",filter);
caseGrid.SetParameter("fetchXML",filter);
Xrm.Page.getControl(gPR)._control.get_innerControl()._element.control.SetParameter("fetchXML",filter);

I've tried setParameter and SetParameter and both yield the same result.

I'm going around the bend trying to figure it out - is it possible that you just can't use SetParameter anymore in CRM 2013 (but you could in 2011)?  If so, how else can I supply the fetchXml for a subgrid?

Tested in IE11, CRM 2013 Update Rollup pack 1 + Service Pack 1. 

Thanks for your time.