Hello,
not pretty sure if this solution works with the form module implemented in WB 2.6.7 (only tested with WB 2.7), but here the steps I am using (WB 2.7):
a) create a new page via Pages Admin and set visibility to hidden (e.g. form_msg.php)
b) add the following code to this code page
var_dump($_SESSION);
echo (isset($_SESSION['field2'])) ?htmlentities($_SESSION['field2']) :'no field 2 submitted';
c) create a page of type form
d) go to the form settings
e) select the page form_msg from the dropdown field success page (at the very end)
f) submit a form and study the output of the Session variables (search for field2-fieldX)
g) adjust the code shown in b) to fit your needs
Regards Christian