SET TERM ^;
CREATE OR ALTER PROCEDURE "SET_GENERATOR"
  (
    "name"  VARCHAR(32) NOT NULL,
    "value" BIGINT
  )
AS
  DECLARE VARIABLE vIncrement BIGINT DEFAULT NULL;
BEGIN
  EXECUTE STATEMENT
      'SELECT GEN_ID("' || :"name" || '", 0) FROM RDB$DATABASE'
    INTO: vIncrement;
  vIncrement = :"value" - vIncrement;
  EXECUTE STATEMENT
      'SELECT GEN_ID("' || :"name" || '", ' || :vIncrement
          || ') FROM RDB$DATABASE'
    INTO: vIncrement;
END^
SET TERM ;^
COMMIT WORK;