[dev] Customer as manditory field - where to look for update customerid

Hello List, we would like to have a customer assigned to a ticket at all time. I asked the German mailing list, but i seem to be unklucky: http://lists.otrs.org/pipermail/otrs-de/2009-February/010884.html Now i started to patch OTRS to include the Fields. I simply added the Fields to the form. Now i simply need to know how to save the CustomerID field. E.g. when submitting AgentTicketCompose, where do i have to look in the code to add/update the CustomerID Field in the ticket? Thanks, Mario