Updating searchIndexValue1,2,etc on an active case

I was able to get this working using this engine code. The auto complete did not have the updateProcessInstance
listed so I didn't see it there. Thanks

ProcessInstanceUpdater piU = new ProcessInstanceUpdater();
piU.setStringIndex1("Value 1");
piU.setStringIndex2("Value 2");
piU.setStringIndex3("Value 3");
piU.setStringIndex4("Value 4");
piU.setStringIndex5("Value 5");
processAPI.updateProcessInstance(p.id, piU);

Hi, I'm trying to update the value of one of the case searchIndexValue strings for an active case.
I see the ProcessInstanceUpdater class has a setStringIndex functions, but it's not clear to me how
to create a ProcessInstanceUpdater object for my specific processInstance. Is this possible?

Hope that makes sense.

Thanks

ross