How to update LOG with custom messages/errors from stored procedure

Hi All,

To Import data, we are using base (seeded) concurrent program
   (WIP  Mass  Load) in stored PL/SQL procedure with the help of
    FND_REQUEST.SUBMIT_REQUEST . The concurrent request import
   records successfully.

Now I want to replace the LOG file ( "View Log" option in concurrent request
  window) with custom message/errors instead of seeded messages/codes .
I want to do the same for debug purpose.

Following is the extracts of my stored procedure.

CREATE OR REPLACE PROCEDURE <PROC-NAME>
BEGIN
           <EXECUTABLE STATEMENTS>
         BEGIN
                FND_GLOBAL.APPS_INITIALIZE ( USER_ID, RESP_ID, APP_ID );
                FND_FILE.PUT_LINE(FND_FILE.LOG,'Concurrent Request Testing ');