Sorry for the late answer, but I have still to digest all the precious info you are bombarding me with.
First of all, the suggestion of Missinglinq is right on target. The table was created importing a sheet from excel, and did not have a primary key. So I reimported it with a primary key, and now the fields are editable. Thank you a lot.
However, there are many suggestions and objections you wrote that I have to study, because they all seem perfectly reasonable, and in any case I am still learning. You see, the purpose of the form is to allow the user to find (and maybe edit) a record in the table using one of three methods: Card number (Stessera), electronic card number (Stesseraelet) and last name (Scognome). The first two should provide only one result (or none, if the card number is wrong); the third, for which user can also input wildcard characters, may give none, one or more results (same last name or same wildcard chars sequence). I can use unbound combo box for the first two, but I cannot (?I think?) for the last name. I'll think about it, and also about all other ideas to simplify things. Thank you all