Contact code that will read your spreadsheet, look up contacts by email address and add or update your My Contacts.
From https://sites.google.com/site/scriptsexamples/learn-by-example/other-examples/contacts-sharing
Example: http://spreadsheets.google.com/ccc?key=0AjThpih7byJUdDZlNGY3TEJPYU9VcWd0TWhaaElfNVE&hl=en