MonInfo
http://www.entechtaiwan.com/util/moninfo.shtm
Phoenix EDID Designer
http://www.tucows.com/preview/329441
Here are some pictures to show what ychng explained.
You need to create a new EDID. Pheonix can extract EDID information from the registry which is useful for reference but contains information that will prevent this from working.
Adding information
Adding more Information. Preferred timing mode ticked means the customised Detailed timings will be used.
In a normal EDID the Standard Timings page would be full but for this mod we need all values unselected. In this image MonInfo is reading from a older monitor EDID which includes the standard timings and native/preferred timing is at 60Hz.
The Detailed Timings page is where you specify the change required whether it be a resolution or refresh rate change. I colour coded it to show which values link. Some numbers are shown differently between the two applications so trial and error might be required to find the relevant values. As you can see from this picture MonInfo is reading from my already customised EDID and the standard timings supported are all missing and the native/preferred timing is at 76Hz.
If you need help finding the corresponding values you can open the EDID from the registry in Phoenix but this also contains all other information so best not to use it as a template.