[IC] passing variables from an HTML page to an Interchange page

[alain abraham]

hello,
I'm seting up a store with a payement gateway (SIPS from ATOS, a french
company).
The CC verification process spend on the bank server. The customer type is
CC number on a page generated by the bank server.

When all is OK, the customer see a page from the bank server saying him that
is transaction is successfull.

In this page there is a form with an hidden fied called "DATA" and a submit
button wich I can customize with a return URL.

I like to know how I can read the value of the DATA variable in a UserTag
(The Usertag is used in the return URL) to update Interchange database.

Merci par avance (Thanks !!).

Oulala