Adding form state

[allenfuller]

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I'm using this package along with the module pattern defined on TMC (here). My one question: where's the right place to add a reactive variable to handle form state? I want to disable the submit button, but can't seem to find the right place to drop in something like template.inProgressVar.set( true );

This:

Template.login.events({
  'submit form' ( event ) {
    template.inProgressVar.set( true );
    event.preventDefault()
  }
});

does not seem to work...

Thanks!