open "pb/spam.cfg"
(if spam.cfg doesn't exist, download the recommended pb configs from the punkbuster forum)

alter;
------------------------------------
//Broadcast your config version every 15 minutes
pb_sv_task 1 900 say PsB SSA Configs - v1.25
pb_sv_task 2 900 say www.punksbusted.com
------------------------------------

to e.g;
------------------------------------
pb_sv_task 10 190 say my first message
pb_sv_task 70 190 say my second message
pb_sv_task 130 190 say my third message
------------------------------------

save your settings, and then restart your server for the settings to take affect

the second number is how many seconds before starting the list over again, the first number is how many seconds to run the message after the list has been started
task1 runs every 10 seconds, after the list has been restarted, e.g. 200 seconds (190 seconds plus the 10 seconds)
task2 runs every 70 seconds, after the list has been restarted
task3 runds every 130 seconds, after the list has been restarted