private System.Timers.Timer timer;
private Random rnd;

private void Form1_Load(object sender, EventArgs e)
{
timer = new System.Timers.Timer(30000);
timer.Elapsed += OnTimedEvent;
rnd = new Random();
}

private void button1_Click(object sender, EventArgs e)
{
timer.Enabled = !timer.Enabled;
}

private void OnTimedEvent(object source, System.Timers.ElapsedEventArgs e)
{
Invoke((Action)delegate
{
int num = rnd.Next(1, 5);
textBox1.Text = num.ToString();
timer.Interval = num * 30000;
});
}
こんな感じなことがやりたいんだと俺は予想するぜ