Sorry, but that's not possible.
mIRC doesn't display keyboard input in the middle of a loop, nor does it interpret scripts other than that in the middle of the loop.
See for yourself:
1. type //while 1 { }
2. type /break (Don't press enter)
3. wait for about a second
4. hit ctrl+break
The second mIRC displays "* Break: command halted" /break will show up in the editbox.
