Related documents in BAM Portal : how to add them in code?

Hello,

I’d like to know how it is possible to add a url to a BAM activity, so that
it appears in the Related Documents section of the BAM Portal. I know how to do it, using the TPE, but here, I need to do it programmatically, because the BAM’ing occurs in csharp code in a pipeline.
The URL needs to be flexible, because I need to pass the messageid of the message to the web application, so that this application can display the message.

Does someone has an idea what methods should be used? (i tried the
AddReference, but this doesn’t work)

I am using the BufferedEventStream class.

Best regards,