What I am looking for is a way to display a message in it's own form
(prefe.) in the GroupWise client.

Is there a way to open a mail item in the mailbox? I.e to view a specific
mail item in the GroupWise client? Can I use ItemOpen() to do that?

What will happen on a successfull ItemOpen()? Will the message open in
GroupWise in it's own form or just be selected in the view or ....?

I have tried the GroupWiseCommander with Execute:
res := vCommander.Execute('ItemOpen('+MessageID+')',outst r);

with no luck. What MessageID should I use in ItemOpen? Can I use the
MessageID string from Message.MessageID found from the Object API?