Inputbox - HELP button not displayed

I'm using the InputBox Method to get a text value from the user. This works fine, but I want to add a help button to the Inputbox.

According to Excel VBA help, the following should display a help button, but it doesn't.

Private Sub CCNProject()
    Dim strProjectNum As String
    Dim strHelpFileName As String
    Dim intHelpTopic As Integer
    
    intHelpTopic = 160
    strHelpFileName = ThisWorkbook.Path & "\SRU.hlp"
   
    strProjectNum = Application.InputBox( _
            prompt:="Enter a two digit project number (01 to 99)", _
            Title:="SRU Create New Project", _
            HelpFile:=strHelpFileName, _
            HelpContextID:=intHelpTopic, _
            Type:=2)
            
End Sub

Anyone have any idea why this isn't displaying the help button?

Found a solution myself: using the InputBox function instead of method:

        strProjectNum = InputBox(prompt:="Enter a two digit project number (01 to 99)", _
            Title:="SRU Create New Project", _
            HelpFile:=strHelpFileName, _
            Context:=intHelpTopic)

This works fine, and although it has the limitations of accepting text only, this is what I want in my case.
Still can't see why the original code doesn't work, though