I haven't used MailChimp but it appears that you can use this REST API like the following:
objHTTP = Create OLEObject
If objHTTP.ConnectToNewObject("MSXML2.ServerXMLHTTP") = 0 Then
objHTTP.Open("GET", ls_RestURI, False)
objHTTP.Send()
objHTTP.DisconnectObject()
Destroy objHTTP
End If