This example displays the number of the bookmark that encloses the beginning of the selection.
MsgBox "Bookmark " & Selection.BookmarkID
This example adds a bookmark named "temp" at the beginning of the document if there's not already a bookmark set for that location.
Set myRange = ActiveDocument.Content
myRange.Collapse Direction:=wdCollapseStart
If myRange.BookmarkID = 0 Then
ActiveDocument.Bookmarks.Add Name:="temp", Range:=myRange
End If