Identify Male or Female Names

We have an excel contact list with the first names 18,000 contacts. We want to populate a field in the data base as male, female or undetermined. We need someone to go through each row of list and determine if the name is a female name, male name or undetermined based on the first name. For example Alice would be a female; John would be a male, while Pat would be undetermined since this name could be Patrick, Pattie or Patricia. Almost all of the names are in English so the person who does the job would need to be very proficient in English.