You could use an on *:Start: { script, which will b executed when you run mIRC.
Add the following script into your remotes (alt + r):

Code:
on *:start: { server irc.dalnet.com -j #cruncher-junkies }


That means that when mIRC loads, The command /server irc.dalnet.com -j #cruncher-junkies will be performed, and you will connect to the server and join the channel.