Allow field to be modified only if...
I have a data field in my batabase that is automatically filled with a date 2 months from another date field. Example:
Last visit date= 01/01/2011 (inserted manually)
Next visit due date= 01/03/2011 (updated automatically)
I know how to make the second field not modifiable, but I would like to allow modifying only after entering a comment on why the date has been changed. My idea would be:
1) a pop-up window opens and asks "Why are you changing the date?";
2) the operator enters some text in the pop-up, which is then saved into a text field;
3) the pop-up closes down and the operator can modify the date field.
If he/she doesn't write anything, a pop-up says "You can't change the date without giving an explanation!", the field stays as it is and can't be modified. Can anyone advise me on how to do this?