Create for instance a file "example.txt" and add a set of commands to it:
window -a "status window" | echo -st starting example
echo -s ...minimizing and restoring mIRC...
showmirc -n
showmirc -r
echo -st done!

Now within mIRC, if you use the following command:
/.play -spc "example.txt" 500
mIRC will execute all commands in that file.

Of course you can put the play command inside a custom alias like:
alias example { .play -spc "example.txt" 500 }
The -c switch tells mIRC to treat all the line in the file as commmands.
The -p switch tells mIRC to give priority to this play request (just in case there are other playbacks running at the moment).
Note that /play requires some target window, therefore I put the -s switch (in mIRC, there will always be a status window).
"500" specifies the per-line playback delay in milliseconds, i.e. the time offset between the different command lines of your file. Note that as the first line in example.txt has two commands on it, there will be no delay in-between the two. You can put "0" for delay to have mIRC execute all the commands without any line delay.

The play command syntax is documented in detail at "playing files" in your mIRC helpfile. For example, you could use an ini-file and have mIRC play a given topic (as the command register, with one or more command line associated to it).