changing refresh rate

after installation I found my refresh rate set at 60 [vertical]- that caused flicker. In order to correct this I had to go to mepis system center-mouse&display-monitor, choosing my monitor from the list. Then I went to Control Center -preipherals-display. 800x600, the resolution I prefer would only permit a 60 refresh rate, so by experimenting I found 834x624 would allow a refresh rate of 75. That fixed my flicker.