How to flush the buffer to trc file

I want to trace the user logins by using a stored procedure. This script (sp_login_trace) is created by the SQL Profiler tool. (Once this procedure works well, I will use sp_procoption to run it automatically everytime the SQL Server startup.)

After I successfully created sp_login_trace, I run it (exec sp_login_trace). The trace process is started and TraceID is 1. (I use select * from ::fn_trace_getinfo(default) to verify it). However the file size of login_trace.trc is always 0 even after I use Query Ananlysis or Eneterprise manager to let some users to login into the SQL Server instance. (when I use SQL Profiler to start a trace, the trace file size will increase along with users continaully login in). At that time if I use SQL Profiler to open the login_trace.trc file, the system will give me an error message: No data since Empty File.

After I stop and delete the trace process, I find that the file size of login_trace.trc becomes 128K and I can see the login records caught by sp_login_trace if I use SQL Profiler to open this file again.

How can I flush the buffer to trc file frequently without need of stopping trace process?

Thanks for helps in advance.

LeonHere is the script of sp_login_trace (Leon)

CREATE PROCEDURE sp_login_trace
AS
BEGIN
/************************************************** **/
/* The following statements contain the SQL Server Profiler-generated */
/* script to create the trace with the required events and data columns. */
/************************************************** **/
-- Create a queue
DECLARE @.rc int
DECLARE @.TraceID int
DECLARE @.maxfilesize bigint
SET @.maxfilesize = 5
EXEC @.rc = sp_trace_create @.TraceID output, 2,
N'C:\Allprojects\SQL_Server_2000\login_trace',
@.maxfilesize, NULL
IF(@.rc != 0) GOTO error

-- You can't script the client-side file and table.
-- Set the events.
declare @.on bit
set @.on = 1
exec sp_trace_setevent @.TraceID, 14, 1, @.on
exec sp_trace_setevent @.TraceID, 14, 6, @.on
exec sp_trace_setevent @.TraceID, 14, 9, @.on
exec sp_trace_setevent @.TraceID, 14, 10, @.on
exec sp_trace_setevent @.TraceID, 14, 11, @.on
exec sp_trace_setevent @.TraceID, 14, 12, @.on
exec sp_trace_setevent @.TraceID, 14, 13, @.on
exec sp_trace_setevent @.TraceID, 14, 14, @.on
exec sp_trace_setevent @.TraceID, 14, 16, @.on
exec sp_trace_setevent @.TraceID, 14, 17, @.on
exec sp_trace_setevent @.TraceID, 14, 18, @.on

-- Set the Filters
declare @.intfilter int
declare @.bigintfilter bigint

exec sp_trace_setfilter @.TraceID, 10, 0, 7, N'SQL Profiler'

-- Set the trace status to start.
EXEC sp_trace_setstatus @.TraceID, 1

GOTO finish

error:
SELECT ErrorCode=@.rc

finish:
END

GOsql