How can you change the parent enumeration dynamicly in an enum control?

We have essentially a multi-tenant deployment of Service Manager.  We have a category field for service requests that has a top level category for each tenant then tenant specific choices below them.  I would like to change the parent enumID in the Enum control to the top level category based on a value in the form.

I can update the value of the data binding with a task handler based on the form value:
app.custom.formTasks.add('ServiceRequest', null, function (formObj, viewModel) {
 formObj.boundReady(function(){
  $('div[data-role="ServiceRequestClassification"]').attr('data-bind',"ciresonDropDownTree: '82777f48-9e32-bcc1-d901-aedd19c2fc53', value: ServiceRequestClassification");
 });
 return;
});

The challenge I have is that the data in the control appears to load prior to the task handler executing.  Is there a way to make the control reload its data?

It looks like most people use hide and show to do this type of thing.  I would prefer not because it could become a scale problem.  It is also possible for our tenants to sometimes open tickets with each other which rules out using the portal's custom forms based on ad group.

Suggestions would be appreciated.

Thanks
Rod