title: The database calculated field not updated, for example total= qte*price when qte or price are updated
body: <p>I designed a Firebird table as below:</p>
  <pre><code>CREATE TABLE LINES
  (
      PK bigint NOT NULL,
      NDOC bigint,
      NART bigint,
      CLOT varchar(10),
      DATE_PER date,
      QTE numeric(18,2),
      Price numeric(7,2),
      PPA numeric(7,2),
  
      CONSTRAINT PK_LIGNES_0 PRIMARY KEY (PK)
  );
  
  ALTER TABLE LINES ADD MNT COMPUTED BY (qte*price);
  </code></pre>
  <p>The data is shown in a dbgrid; when I update qte or price the field MNT does not get updated.</p>