Multiple Search Criteria on Search Form

We have created a saved search that looks up a custom field called "sub lot number" which is a field in a custom record. We are using the saved search as a search form to allow users vary the search criteria each time the search is executed.

We are able to enter and search for a single sub lot number at a time but if we enter more than one sub lot number separated by a comma, the search form fails and we get the message "No Search Results Match Your Criteria".

We have tried using "Any", "Contains", "Not Empty" with the search criteria separated by commas but without success.