How to get Google Maps route planner on website's iframe

How to get Google Maps route planner on website's iframe

I'm programming a new (wordpress) website and there is a "Contact" menu
item. In this menu item I got a map (code by Google Maps iframe). Now I
should have a route planner under the map. For this I got a little code:
<form name="search_route" method="get" action="http://maps.google.com/"
target="_blank">
<input name="saddr" type="text" id="saddr">
<input name="daddr" type="hidden" id="daddr" value="Empire State
Building, 350 5th Avenue, New York, NY, USA">
<input type="submit" name="Submit" value="Submit">
</form>
My problem: The code is working, but it links to maps.google.com like I
told the form. But the route should plan on the iframe I got on the page
and not open another link. Is this possible? If yes, can someone give me a
hint?
Thanks in advance
Cheers