1) The entire script wasn't necessary, just the part where the dialog is actually layed out.
2) Please use the Code Tags in future when posting code.
The problem, is stated in the error message. mIRC will not allow you to run a dialog without some kind of an OK or Cancel button. These don't have to be named that, but they do have to be present. If you don't want one, for some reason, you can always put it in, then hide it
Alternatively you do have a menu with an Exit command, which you could set to act as OK and/or Cancel
Normally OK would be coded to save any changes made, and Cancel would void any changes made, but this is not a requirement.
With your code, I would recommend changing
item "&Exit", 476, 403
to
item "&Exit", 476, 403, ok
or
item "&Exit", 476, 403, cancel
depending on if you want the Exit to act as OK or Cancel
Just changing that one line is all that's required at this point.
