Hello Elad,
Well.. there are two scenarios here:
1. If you open the second session from the first one. It's easy, you just send the structure as the HTTP request:
http://<url>:<port>/sap../something/.../<application_name>?<field name>=<value>&...
For example:
?DOKAR=PDM&DOKNR=1234567&DOKTL=001....
2. If however, you have completely different session.. the only solution that comes in mind is Shared Memory Objects. You can find more details about this here:
Shared Objects - Implementation (SAP Library - ABAP - Shared Objects)
or a short tutorial...
Hope it helps! Or maybe, you can give some more details. This is a very interesting topic!
Tudor