Once a GoldMine installation has been customized, fields added, and everything made perfect; nothing is more frustrating than watching the precious values in your custom fields become missing or wrong. So, if you'd like to keep a careful eye on who is changing which field to what, simply enable the history change log for the field in question.
To do this, you must be a MASTER user.
Go into "Screen Design Mode", by right-clicking on the contact record and selecting "Screen Design".
Double click on the field you want to track.
Go to the "Security" tab.
Click the box labeled "Log Changes in History".
Keep in mind this setting is system wide; so the very next time the field is changed for a contact record, you will get a resulting history item that tracks the last value and the current value.