Connect to SFTP directory using Excel, VBA and .ppk key file?

Question

I'm trying to connect to an SFTP directory using VBA within Excel. I would like to drop off and retrieve files from the directory. Currently I do this by dragging/dropping with Filezilla, but I'd like to see if I can achieve this using VBA so that users do not have to exit Excel and can send/retrieve files to/from the remote directory without having to leave Excel and go to Filezilla.

I tried using some VBA with putty's PCSP.exe tool but had no joy. I tried to adapt the code below that I found elsewhere.

Public Sub SftpPut()
    Const cstrSftp As String = """U:\putty\pscp.exe"""
    Dim strCommand As String
    Dim pUser As String
    Dim pPass As String
    Dim pHost As String
    Dim pFile As String
    Dim pRemotePath As String

    pUser = "---"
    pPass = "---"
    pHost = "---"
    pFile = "C:\Access\sample.txt"
    pRemotePath = "/home"

    strCommand = cstrSftp & " -sftp -l " & pUser & " -pw " & pPass & _
        " " & pFile & " " & pHost & ":" & pRemotePath
    Debug.Print strCommand
    Shell strCommand, 1 ' vbNormalFocus '
End Sub

When using Filezilla, I login with a User ID and a .ppk Key File, I can't see how to use the Key File with the above.

Can anybody assist? Many Thanks.