Programatically submit form

I have a form with lots of formviews and texboxes.  The first few formviews are read only and are populated from a dropdown list select command.  Based on the results entered into the formviews several other dropped down lists are populated.  This requires hitting the submit button twice; once to populate the forms and then again to populate the dropdwn lists from the formview values.  How can I programmatically simulate the clicking of the submit button the second time using an onclick script?
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