[Users] Adding new header fields to Status message (Registrar/200 OK)?

Hi, Again, complete newbie question (honestly, I searched the OpenSER and SER archives and did not find an answer ;): (How) can OpenSER add a new header field into the registrar's 200 OK status message in reply to a successful REGISTER? (New header field meaning that the header line was not present in the REGISTER). What I tried so far is to add the field in two ways: - Added the field to the incoming REGISTER message while doing the main processing using append_hf(). The new header field is not included into the 200 OK. - Added the field within the OnReply_Route[1] block (triggered). But apparently OpenSER does invoke the OnReply_Route only for incoming status messages. When the code is invoked by a proxy on traversing status messages it works perfectly, for the registrar it does not. Any idea how to modify Registrar-outgoing status messages? Many thanks in advance, --Joachim