You can save a text file in your mirc's directory, then type /play yourfile.txt and it will play the content of it in the main channel you're located. (I'm not certain if you can play a file through the private message.)
Alternatively, you can use your mirc popups (pressing ALT + P together) and place this little snippet in:
Play File { .play $$sfile(Please Choose a File to play,Ok) 1000 }
Then you can right click on your nicklist to trgger it. It will play a text file content located per your selection line by line with a 1000m delay. The channel popups will work as well if you choose to place the snippet there.