THUMBBUTTON Structure

[StructLayout(LayoutKind.Sequential,
     Pack = 8,
     CharSet = CharSet.Unicode)]
 public struct THUMBBUTTON
 {
     public const int THBN_CLICKED = 0x1800;
     public THB dwMask;
     public uint iId;
     public uint iBitmap;
     public IntPtr hIcon;
 
     [MarshalAs(UnmanagedType.ByValTStr,
         SizeConst = 260)]
     public string szTip;
 
     public THBF dwFlags;
 }