Did you change the values (repeated below) to reflect what you have? You said that the workbook attachment always has the same name, so put that name where shown below. The other values reflect values I cannot know without seeing the workbook, so change those as required.
Const strWorkBook As String = "
WorkBookName.xlsx" 'The name of the attached workbook
Const strSheet As String = "
Sheet1" 'The name of the worksheet to process
Const strCell As String = "
B1" 'The cell to process
Const iCount As Integer =
20 'The threshold value of the above cell
Const strMessage As String = "
This is the reply message body text."
The message created was a reply to the message received with the attachment, so the recipient will be the sender of that message. I take it that you want to send it on to others rather than reply? If that is the case, change the lines
Set olMail = olItem.Reply
With olMail
to
Set olMail = olItem.Forward
With olMail
.To = "
someone@somewhere.com; someoneelse@somewhereelse.com"
where the recipients are the addresses in bold, separated by semi-colons.