Start Event trigger filters

When trying to set a conditional start option for date, you are only able to set a "SET" date. it cannot be a variable or a context item, like [TODAY]. In my use case I have a workflow executing when an opportunity in MSCRM has been moved to a certain stage. I don't want the workflow to execute if the stage was change yesterday and the the record has been updated and still on that same stage. Placing a time constraint will solve this as I know exactly when the stage was set.