>I tend not to use explicit Edit mode. If a user want to edit some data he (or she) clicks (or tabs right to it) the data and changes it. All the changed data is coloring red just to let user see wich data has been changed. If the user want to undo the data, just click the undo button and the data is coloring blue again.(In my program editable data is colored blue, changed data is colored red, non-editable data is colored black)
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Now that's a neat idea. How, may I ask do you colour the changed data? Also, how do your users save the data? Is it done with a buttton or in the valid of each object?

The data is saved when the users choose another record or closes the form. It can also be done explicitly by clicking a savebutton on the toolbar. They can also choose to undo the changes by clicking a button on the toolbar (also a menu choice with hotkey).