oracle - トリガー内でPL/SQL関数を呼び出す方法は?

Question

SQL> CREATE OR REPLACE TRIGGER INSERT_DATACOL
  2  AFTER insert ON FIELDWORKER_INFO for each row 
  3  declare
  4  FW NUMBER;
  5  begin 
  6  FW := datacol_insert_fwkr(:OLD.FIELDWORKER); 
  7  end; 
  8  /

Warning: Trigger created with compilation errors.

SQL> show err
Errors for TRIGGER INSERT_DATACOL:

LINE/COL ERROR
-------- -----------------------------------------------------------------
4/1      PL/SQL: Statement ignored
4/7      PLS-00201: identifier 'DATACOL_INSERT_FWKR' must be declared