For a useful introduction to Microsoft Excel and its functions, try: Spreadsheet Projects in Excel for Advanced Level, Julian Mott and Ian Rendell (2003). Oxford: Hodder Murray.
The most authoritative text on the subject is: Strategic Benchmarking: How to Rate Your Company’s Performance against the World’s Best, G.H. Watson (1993). New York: John Wiley & Sons.
For an excellent overview, try: Financial Times Briefing: Change Management, Richard Newton (2010). Harlow: Financial Times Prentice Hall.
One of the seminal works on coaching: The Tao of Coaching, Max Landsberg (2003, revised edition). London: Profile Books.