size = 3;
arbitrary_maximum = 5;

function populate () {
  ajax = new Ajax.Updater('text', "/plan/bingo.cgi?l="+size,
	{ asynchronous: true });
}

function down_clicked () {
  if (--size <= 0) {
    size = 1;
  }
  populate();
}

function up_clicked () {
  if (++size >= arbitrary_maximum) {
    size = arbitrary_maximum;
  }
  populate();
}