The file DBGHELP.DLL is needed for RtPlot to create a small dump file if it crashes, to assist in finding the reason for the crash. In some distributions it was mistakenly not included. It can be downloaded from Microsoft web and probably from other sources on the web. The package on RtPlot web includes version 5.1.2600.0 of this file.
Close and reopen the data file. Assuming that f is a file pointer (i.e. FILE *) and the file name is data.txt. After adding a line of data do:
fclose(f);
f = fopen("data.txt", "a"); /* Close and reopen in append mode */
This normally forces the OS to update the write time of the file.
HANDLE h = (HANDLE) (_get_osfhandle(_fileno(f) ) );
After you write your data, flush the buffer:
fflush(f);
Then update the write time:
FILETIME write_time;
GetSystemTimeAsFileTime(&write_time_);
SetFileTime(h, NULL, NULL, &write_time);
That should do it.
Alternatively, you can try to use a port of the UNIX utility touch. Doing touch data.txt from the command prompt will update the write time of the data file "data.txt". You can create a batch file to update periodically the write time of "data.txt".
For more information see Cooperating with RtPlot section of the documentation.
Try turning off Data tips by unchecking it in the contex menu. When Data tips is on, RtPlot needs to test if the cursor is near a data point, so that it knows to show the coordinates. This may consume too much CPU on very big files.