From Macros Wiki
- ON_DROPDOWN <dropdown number>, <index>, <control to change>, <new state>
- Change the state of a dialog control, based on the current index of a dropdown menu.
- <dropdown number>
- Dropdown menu number
- The index to the dropdown menu, 1 for the 1st item, 2 for the 2nd.
- <control to change>
- The state must be one of SHOW, HIDE, ENABLE or DISABLE.
- <new state>
- ON_DROPDOWN 2, 5, INPUT4, DISABLE
- This will enable the 4th input box when the 5th item on the 2nd dropdown menu is selected.
- The opposite also applies, the input box will be disabled when any other item on the dropdown is selected.