arcgis desktop - Auto populating field in attribute table, using several fields of record information from another table?

I have an attribute table with one field that needs to be populated, but because there are thousands of records, I would like to know a way that it can be done somewhat automatically. The information that the field needs to be populated with is currently stored in an excel table (this can be changed if necessary). In order to populate the fields correctly there are several other fields that need to match information in the fields within the attribute table. Because there are multiple fields that need to match, I cannot get a join to work.