I use many globals. Took a bit if experimentation to do it
correctly. I find the MSDN and microsoft.support sites good for my
level of experience (Advanced beginner - not a professional
programmer).

Here's a couple of links for MSDN:
http://msdn.microsoft.com/library/

http://msdn.microsoft.com/library/default.asp?url=/library/en-
us/vbref/html/vbmscLROverview.asp

Microsoft support, searching on VBA gets you to the knowledge base:
www.support.microsoft.com/.../default.aspx?qu=VBA

Globals:

Snipped from my serial I/O spreadsheet:


In the declarations section of a module
=======================================
Option Explicit
Public com_port As Long
Public BailOut As Long
Public PortName As String
Public BaudStr As String
Public xerr As Boolean
Public data_msg As String
Public data_in As String
Public totalread As Long
Public r As Integer
Public pref As String
Public suff As String
Public AnswerLength As Integer
Public radio_address As Integer
Public j As Integer
Public Cmd As String