Populate Lookup field based on related entity value
In the last week I have seen at least three posts of requests on how to populate a lookup field based on a value of a text field that is supposed to search for the same data in a related entity. I am not going to delve on whether or not what you are trying to do is the correct choice, as I don’t have your exact set of requirements, but I will explain how to perform the functions that you are looking for.