Anon,

Try getting the rectangle associated with the control and use its Left and
Bottom properties.

For example:

private void MyControl_MouseUp( object sender, MouseEventArgs e )
{
  if ( e.Button == MouseButtons.Right )
  {
     Point pt = new Point( this.ClientRectangle.Left,
this.ClientRectangle.Bottom );
     this.contextMenu.MenuItems.Add( this.helpItem );
     this.contextMenu.MenuItems.Add( this.scpiItem );
     this.contextMenu.Show( this, pt );
     this.contextMenu.MenuItems.Clear();
  }
}

Hope that helps,
Dave