1. Write a script to append all keyword URLs with a specific ID code.
2. On the webpage, show that code below the phone number.
3. When someone calls, have the sales people ask for the ID code.
4. When someone uses your contact form, pass the code into the email.
5. You'll have to find a good way based on your intranet/sales process/etc to associate the codes with sales/contacts.
6. Correlate the ID codes (along w/ sales/contacts) back to the original keywords to see ROI by keyword.
This should be able to close the loop between online advertising and offline sales.