Add a journal entry/note after I interact with a locked door?

[Pandemoneus]

Call a
SetEntityPlayerInteractCallback(string& asName, string& asCallback, bool abRemoveOnInteraction);
when you lock the door.
Create another function as target of this callback and put a
SetMessage(string &asTextCategory, string &asTextEntry, float afTime);
inside.

I think your scripting knowledge is good enough to deal with these two hints.