Add bookmarks to pdf file using Excel VBA

Good morning -

I have, through internet searches, created an Excel macro that prints numerous workbooks to pdf, combines them into one file and prints that file.  I have been searching for the last piece, which is adding bookmarks, but have not had any luck getting any of it to work.  The following is the code that I am using to add the bookmarks -

Dim avdoc, pddoc, app As Object
Dim stFile As String
Dim btitle As Boolean
Dim PDBookmark As CAcroPDBookmark

stFile = "D:\Test\Test.pdf"
Set app = CreateObject("AcroExch.app")

Set avdoc = CreateObject("AcroExch.AVDoc")
Set pddoc = CreateObject("AcroExch.PDDoc")
pddoc.Open stFile

Set avdoc = pddoc.OpenAVDoc(stFile)
Set PDBookmark = CreateObject("AcroExch.PDBookmark", "")

app.MenuItemExecute ("NewBookmark")

btitle = PDBookmark.SetTitle("Test Bookmark")

This code does insert a bookmark on the first page of the document.  The bookmark title displays as Untitled instead of Test Bookmark as the code states.  Can someone answer the following questions -

1.  Why is the code not changing the bookmark from Untitled to Test Bookmark, and

2.  How would I nodify the above code to go to a certain page then enter the bookmark.

All help is greatly appreciated.  Thanks in advance for your time.