Hi Hermann
When I need something like this, I work with range objects. Declare two range objects. Assign one of them to the bookmark range. Assign the other to that Range's Duplicate. Roughly (off the top of my head, untested)
Dim rngB1 as Word.Range
Dim rngB2 as Word.Range
rngB1 = doc.Bookmarks("Content").Range
rngB2 = rngB1.Duplicate
Then I'd probably continue like this
rngB2.InsertBefore " "
rngB2.Collapse Word.WdCollapseDirection.wdCollapseStart
'Should put the range in front of the space
rngB2.Text = "The new content"
doc.Bookmarks.Add(rngB2, "NewContent")