I would think that a simple method would be something like an onSubmit caller function. It would go something like this
<form name='my_form' action='whatever' method='post' onSubmit='return geocode_function(address);'>
then make sure you have the javascript geocode_function(name it whatever you want) function created...
geocode_function(address_info)
{
send the address_info variable to google, and retrieve the info they give back to you.
then I would recommend that you change a hidden value in your form, such as:
in the form-><input type='hidden' name='geocode'/>
in your javascript->document.my_form.geocode.value='whatever you retrieved from google';
then, after you have set that info, make sure you have:
return true;
at the end of your javascript function.
Basically what happens is that the user clicks submit, the data is passed to google, then google processes and returns the geocode data, you then add this data to the form via javascript, and then the return true tells the form that everything is ok and that it can now submit the form to the next place.
Then, on the page the receives the form, you simply retrieve the information from that hidden form element.
Hope this helps, but if not, I'd be happy to construct a working model, but I'll need some source code from you.
Exactly where is the point that you are assassinated rather than murdered?