With CyberGraphX? You should just be able run (just boots up my A4000 on a Viewsonic to check) CGXMode in Prefs and edit the "Monitor Specification" via the Edit button.
Once in there, you should specify the values from your Monitor handbook regarding the Horizontal and Vertical frequenceys. If the monitor tells you the Syncronisation settings, enter them too.
If you haven't got the monitor specs, email the TFT monitor manufacturers and ask them.
