How to use OpenEventLog?

Edited text of question

According to the documentation, the second parameter of OpenEventLog "can be the Application, Security, or System logfile, or a custom registered logfile. If a custom registered logfile name cannot be found, the event logging service opens the Application logfile, however, there will be no associated message or category string file." I think the parameter is not for a source name. In your case, you actually opened the Application logfile.

Chensu, to go over one point you said concerning it opening up the Application logfile, it didn't. If I look into the Event Log I match what my app  has printed with entries in the System log including strings. The source name I specified is ( like I mentioned in the original message) a valid subkey of the System logfile.

So OpenEventLog opens up either the Application, the Security or the System logfile. I assumed it would go further and return only the records associated with the source name I specified. For example, if I specified "EiconCards", I expected only records in the System log that dealt with "EiconCards".  Hence, I must parse thru each record in the System log to look for the corresponding "EiconCards" records. (Sounds time-consuming and I must keep the System log clean at all times to enhance performance.  I will try to implement NotifyChangeEventLog to avoid queries)

If there is anything you can add I will appreciate it otherwise let us close this question and thanks again.

Just in case you haven't read it, I copied the following example useful for you from the documentation.

Reading the Event Log
The following example reads all the records in the Application log file and displays the event identifier, event type, and event source for each event log entry.

void DisplayEntries( )
{
    HANDLE h;
    EVENTLOGRECORD *pevlr;
    BYTE bBuffer[BUFFER_SIZE];
    DWORD dwRead, dwNeeded, cRecords, dwThisRecord = 0;
 
    // Open the Application event log.
 
    h = OpenEventLog( NULL,             // use local computer
             "Application");   // source name
    if (h == NULL)
        ErrorExit("Could not open the Application event log.");
 
    pevlr = (EVENTLOGRECORD *) &bBuffer;
 
    // Opening the event log positions the file pointer for this
    // handle at the beginning of the log. Read the records
    // sequentially until there are no more.
 
    while (ReadEventLog(h,                // event log handle
                EVENTLOG_FORWARDS_READ |  // reads forward
                EVENTLOG_SEQUENTIAL_READ, // sequential read
                0,            // ignored for sequential reads
                pevlr,        // pointer to buffer
                BUFFER_SIZE,  // size of buffer
                &dwRead,      // number of bytes read
                &dwNeeded))   // bytes in next record
    {
        while (dwRead > 0)
        {
            // Print the event identifier, type, and source name.
            // The source name is just past the end of the
            // formal structure.
 
            printf("%02d  Event ID: 0x%08X ",
                dwThisRecord++, pevlr->EventID);
            printf("EventType: %d Source: %s\n",
                pevlr->EventType, (LPSTR) ((LPBYTE) pevlr +
                sizeof(EVENTLOGRECORD)));
 
            dwRead -= pevlr->Length;
            pevlr = (EVENTLOGRECORD *)
                ((LPBYTE) pevlr + pevlr->Length);
        }
 
        pevlr = (EVENTLOGRECORD *) &bBuffer;
    }
 
    CloseEventLog(h);
}

I have seen and read this sample code and it did come in handy.  (BUFFER_SIZE ?)

The documentation does not say the value of BUFFER_SIZE. It may be 1024 or 2048.

Thanks AlanB. You suggestions are accurate but I have completed this problem already. I did want Chensu to close it ( see 2nd Comment before this one) because I was done with this issue. Thanks anyway.