"Dock" a WinForm beside another WinForm

This code sort of "docks" a WinForm to the left side of another. When you see what I am doing, you will see that this is actually pretty simple. It's a cool look and you can change it in your own way to dock to top/right/bottom. There's nothing to do on the "parent" form and here's the code for the "child" form:

using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;

public partial class ChildForm : Form
{
    Form m_ParentForm;
    public ChildForm(Form parentForm)
    {
        InitializeComponent();
        m_ParentForm = parentForm;

        // setup 

        m_ParentForm.Left = m_ParentForm.Left + (this.Width / 2);
        Reposition(null, null);
        m_ParentForm.Activated += new EventHandler(Reposition);
        m_ParentForm.Move += new EventHandler(Reposition);
        m_ParentForm.ResizeEnd += new EventHandler(Reposition);
        m_ParentForm.FormClosing += new FormClosingEventHandler(ParentForm_FormClosing);
        this.FormClosing += new FormClosingEventHandler(ChildForm_FormClosing);
    }

    void ChildForm_FormClosing(object sender, FormClosingEventArgs e)
    {
        m_ParentForm.Activated -= new EventHandler(Reposition);
        m_ParentForm.Move -= new EventHandler(Reposition);
        m_ParentForm.ResizeEnd -= new EventHandler(Reposition);
        m_ParentForm.FormClosing -= new FormClosingEventHandler(m_ParentForm_FormClosing);
    }

    void ParentForm_FormClosing(object sender, FormClosingEventArgs e)
    {
        this.Close();
    }

    void Reposition(object sender, EventArgs e)
    {
        this.Height = m_ParentForm.Height;
        this.Top = m_ParentForm.Top;
        this.Left = m_ParentForm.Left - this.Width - 5;
        // z index
        SetWindowPos((int)this.Handle,
            (int)m_ParentForm.Handle,
            0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_SHOWWINDOW | SWP_NOACTIVATE);
    }

    [DllImport("user32.dll", EntryPoint = "SetWindowPos")]
    public static extern bool SetWindowPos(
        int hWnd, // window handle
        int hWndInsertAfter, // placement-order handle
        int X, // horizontal position
        int Y, // vertical position
        int cx, // width
        int cy, // height
        uint uFlags); // window positioning flags
    const uint SWP_NOSIZE = 0x1;
    const uint SWP_NOMOVE = 0x2;
    const uint SWP_SHOWWINDOW = 0x40;
    const uint SWP_NOACTIVATE = 0x10;
}