Thanks Mike!
Your solution works fine. I still have some questions about why VBA code has to be so ugly and unlogical but it'll do for now.
It seems (I haven't got a clue why) that the "+1" is unnecessary, the range automagically adapts to the right length.
This is the code I went with:
Dim r As Range
With ActiveDocument
.Bookmarks.Add ("test")
Set r = .Range(Start:=.Bookmarks("test").Range.End, End:=.Bookmarks("test").Range.End)
r.InsertAfter "Aaa"
r.InsertAfter "Beee"
r.InsertAfter = "Cee"
End With
If anybody has a good pointer about the structure of Word documents (its navigation concepts, i.e. what and why is a "Range"), then I'm happy to receive some pointers.