There is an old Feature Request from January about improving/extending the functionality of the Economic Calendar for automated strategies, as currently (just as Support replied) you cannot 'read' the impact parameter of a calender event.
Also currently it is not possible that a strategy, without any user interaction, processes economic calendar messages, so basically you cannot build a strategy with the JForex-API that is based on (or using) Economic Calendar events. If you think that this must be changed, please take a look on the above mentioned
feature request, and make yourself heard.
@support:
Is there any chance that this feature will be available? I think there is interest for this among users (just take a look on the view count).