C#

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
 
public class VolumeControl : TrackBar
{
  [DllImport("winmm.dll")]
  private static extern int waveOutSetVolume(IntPtr device, UInt32 vol);
 
  public VolumeControl()
  {
    base.Minimum = 0;
    base.Maximum = 0xffff; // Left & right volume is 16bit each
    base.TickFrequency = 4096;
    base.SmallChange = 4096;
    base.LargeChange = 8192;

    this.ValueChanged += new EventHandler(VolumeControl_ValueChanged);
  }
 
  private void VolumeControl_ValueChanged(object sender, EventArgs e)
  {
    // Left volume in lower 16bit, right volume in upper 16bit
    // IntPtr.Zero => Default Device/Master volume
    waveOutSetVolume(IntPtr.Zero, (uint)(Value|Value<<16));
  }
}

private void button_Click(object sender, System.EventArgs e)
{
    Cusor oldCursor = Cursor.Current;
    try
    {
        Cursor.Current = Cursors.WaitCursor;
        //
        // Do your lengthly mojo here
        //
    }
    finally
    {
        Cursor.Current = oldCursor;
    }
}