Add Bookmark

This Word macro will add a bookmark:

Sub AddBookmark()
    ActiveDocument.Bookmarks.Add "automateexcel_com_01"
End Sub

Delete Bookmark

This VBA macro will delete a bookmark:

Sub DeleteBookmark()
    If ActiveDocument.Bookmarks.Exists("automateexcel_com_01") Then    'we need to check if bookmark named "automateexcel_com_01" exists in active doc
        ActiveDocument.Bookmarks(Index:="automateexcel_com_01").Delete
    End If
End Sub
AutoMacro - VBA Code Generator

Go To Bookmark

This simple macro will go to a bookmark:

Sub GoToBookmark()
    If ActiveDocument.Bookmarks.Exists("automateexcel_com_01") Then    'we need to check if bookmark named "automateexcel_com_01" exists in active doc
        Selection.GoTo What:=wdGoToBookmark, Name:="automateexcel_com_01"
    End If
End Sub

Modify Bookmark

This macro will modify a bookmark’s content:

Sub ModifyBookmarkContent()
' change bookmark contents
' more complicated, because changing bookmark range content will delete bookmark
    Dim oRangeBKM As Range

    If ActiveDocument.Bookmarks.Exists("automateexcel_com_01") Then    'we need to check if bookmark named "automateexcel_com_01" exists in active doc
        'Identify current Bookmark range and insert text
        Set oRangeBKM = ActiveDocument.Bookmarks("automateexcel_com_01").Range
        oRangeBKM.Text = "automateexcel.com"
        'Make again the bookmark
        ActiveDocument.Bookmarks.Add "automateexcel_com_01", oRangeBKM
    End If
End Sub

This is a modify bookmark function:

Sub UpdateBookmarkContent(strBookMarkName As String, strNewText As String)
' "usable' procedure for add in
    Dim oRangeBKM As Range

    If ActiveDocument.Bookmarks.Exists(strBookMarkName) Then    'we need to check if bookmark named "automateexcel_com_01" exists in active doc
        'Identify current Bookmark range and insert text
        Set oRangeBKM = ActiveDocument.Bookmarks(strBookMarkName).Range
        oRangeBKM.Text = strNewText
        'Make again the bookmark
        ActiveDocument.Bookmarks.Add strBookMarkName, oRangeBKM
    End If
End Sub

You can call the function by adding the bookmark name and new text as arguments:

Sub CallBookmarkFunction()

    Call UpdateBookmarkContent("automateexcel_com_01", "automateexcel.com")

End Sub