For it to work, Khaled would need to allow multiple spacing sequences so you can do the "whitepace" needed to push it over..
+---------------------------------------------------------+
| Uber ASCII Dialog >:P [_][[]][X] |
+---------------------------------------------------------+
| My Listbox |
| +-----------------------------------------------------+ |
| | . . . . . . . . . . . . . . . . . . .This Is Item 1 | |
| | . . . . . . . . . . . . . . . . . . .Item 2 Is Here | |
| | . . . . . . . . . . . . . . . .This would be item 3 | |
| | . . . . . . . . . . . . . . . . . . . . . . . . etc | |
| | | |
| | | |
| +-----------------------------------------------------+ |
| |
| [ CANCEL ][ OKAY ] |
| |
+---------------------------------------------------------+
the ". . . ." are of course spaces. You cant send all those spaces to mirc, so its not really possible. unless Khaled made an eception to the /did command.
Also, if you wanted mIRC to do it on its own, Khaled would have to know how many spaces a ccross your dialog is (using the width as a reference), then could do a facsimileof "padding" the string, and changing the font.