A careful use of timers usually does the trick. If that fails you can use the sleep alias. Though, most consider it bad coding to need to resort to it.

Code:
/sleep {
  var %a = $ticks $+ .wsf
  write %a <job id="js"><script language="jscript">WScript.Sleep( $+ $$1 $+ );</script></job>
  .comopen %a WScript.Shell
  if !$comerr { .comclose %a $com(%a,Run,3,bstr,%a,uint,0,bool,true) }
  .remove %a
}


Usage /sleep N

N is the number of milliseconds you'd like to pause mirc for.

Yar