You would have to do a search of the text file. If the file becomes large, this will take a lot of time and start playing havoc on your mirc. If you want to incorporate that, you need to start looking for alternative ways to store. In this case, a window might be easiest. Or a hashtable. In either case, a textfile is still possible provided you change the way the information is stored. I'd start off every line written to it with a word consisting of nick and ctime >> $+($nick,$ctime) << to make for easy searching. The way you store stuff now is gonna make that extremely tedious and time consuming, especially if ythe file gets bigger.
You could make something similar for text files
