Widget Form Pass Data to Larger Form

How can I configure a widget form to pass data onto a larger, full size form?

For example, if someone puts information, like their name, into a widget form, clicking next would take them to the second step of a full size form, with the first step being completed (in this case the users name).

Generally this would be easy (using the $_POST global var) but the full form is going to be a multi-step form so its not just a matter of populating fields on the current step, I need to populate fields on the first step.

Any help would be appreciated.

After reading the docs, I came up with a solution using the gform_field_value_$value filter.

Here's my code (sorry, no idea how to post code snippets):

http://www.pastie.org/2379144

I just made a custom form and set it to post to the full form page.

http://www.pastie.org/2379159

This is from my functions.php.

Just set the variables and you should be set to go. For anyone wanting to use the gravity forms widget, Chris' solution should work.

Thanks for the help.