[jQuery] AutoComplete and Validation

Hello,
I am using AutoComplete with Validation. Can I create a validation
that accepts only values from the autocomplete?
For example if the autocomplete list is:
"New York, London, Lisbon, Paris"
Then the following would be accepted:
"New York, London"
"New York"
"Lisbon, Paris "
" London,Paris,Lisbon"
But not:
"New York, Rome"
"Moscow"
Is this possible?
Thanks,
Miguel