Excel VBA Web Scraping - vba

Question

I'm new to Excel VBA programming and need some help to debug my code for web scraping some data off of Amazon.
On my sheet1, I am listing the asins of products and trying to use this code to complete the URL to land onto the product page, then will the sales rank of the product via class ID or another html tag.
However, I keep getting the error:
User-Defined Type not Defined
I can't figure out where the bug is.
The code is listed below:
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Row = Range("azAsin").Row And Target.Column = Range("azAsin").Column Then
Dim IE As New InternetExplorer
IE.Visible = True
IE.Navigate "https://www.amazon.com/dp/" & Range("azAsin").Value
Do
DoEvents
Loop Until IE.readyState = READYSTATE_COMPLETE
Dim pap As HTMLDocument
Set pap = IE.document
Dim sDoc As String
sDoc = Doc.getElementsById("SalesRank")
MsgBox sDoc
End If
End Sub

Answer 1

Try this:
Dim ie As Object
Set ie = CreateObject("InternetExplorer.Application")
ie.Visible = True
'...
Dim objRank as Object
Set objRank = ie.Document.getElementById("SalesRank")
Dim rank As String
If Not objRank Is Nothing Then rank = objRank.innerText

Answer 2

Here is a fully latebound version that also removes the need for a browser.
Observations on your code:
The other answer has corrected, but not mentioned, that in your existing script you attempt:
Dim sDoc As String
Doc = Doc.getElementsById("SalesRank")
getElementsById is invalid as Id should be singular and the syntax is getElementById. This will also return an object, not a string. so you would need ie.Document.getElementById("SalesRank").innerText to get a string; though it is better to set to an object first and test If Not obj Is Nothing Then, as indeed the former answerer has done.
Code:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim html As Object, i As Long, URL As String
URL = "https://www.amazon.com/dp/" & Range("azAsin").Value
If Target.Row = Range("azAsin").Row And Target.Column = Range("azAsin").Column Then
With CreateObject("MSXML2.serverXMLHTTP")
.Open "GET", URL, False
.send
Set html = CreateObject("HTMLFile")
html.body.innerHTML = .responseText
End With
For i = 0 To html.all.Length - 1
If html.all(i).ID = "SalesRank" Then MsgBox html.all(i).innerText
Next i
End If
End Sub