Range.BookmarkID (Word)

Returns the number of the bookmark that encloses the beginning of the specified range; returns 0 (zero) if there is no corresponding bookmark.

The number or the bookmark corresponds to the position of the bookmark in the document: 1 for the first bookmark, 2 for the second one, and so on.

Set myRange = ActiveDocument.Content 
myRange.Collapse Direction:=wdCollapseStart 
If myRange.BookmarkID = 0 Then 
 ActiveDocument.Bookmarks.Add Name:="temp", Range:=myRange 
End If