if(menuItem13.Checked)selectnum = MyPlayer.NextPlay(0);
else if (menuItem15.Checked)selectnum = MyPlayer.NextPlay(1);
else if (menuItem16.Checked)selectnum = MyPlayer.NextPlay(2);
else if (menuItem17.Checked)selectnum = MyPlayer.NextPlay(3);
if(selectnum != 0)
{
listBox1.SelectedIndex = selectnum - 1;
MyPlayer.play(selectnum);
}
}