Why is it so difficult to set the location of splitter?

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C#

VB

Hi everyone,
The content of the codes given below; 3 panels and 2 Splitter are required. However, the 2nd splitter (Green) must be located between the gray and brown panel. But not in the right place. Are there any suggestions? Thanks.

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Show()

        Dim tmpSplitter As Splitter
        Dim tmpPanel As Panel
        Dim MainPanel As Panel

        ' This is main panel
        '
        MainPanel = New Panel
        With MainPanel
            .Name = "MainPanel"
            .Dock = DockStyle.Fill
            .BackColor = Color.LightGray
            .BorderStyle = BorderStyle.Fixed3D
            .Visible = True
        End With
        Me.Controls.Add(MainPanel)

        ' 1: First Top Panel and Splitter 
        '
        tmpPanel = New Panel
        With tmpPanel
            .Name = "Panel1"
            .Dock = DockStyle.Top
            .BackColor = Color.Red
            .Visible = True
        End With

        tmpSplitter = New Splitter
        With tmpSplitter
            .Name = "Split1"
            .Dock = DockStyle.Top
            .BackColor = Color.Blue
            .Cursor = Cursors.HSplit
        End With

        Me.Controls.Add(tmpSplitter)
        Me.Controls.Add(tmpPanel)


        ' 2: Second Panel added to the left side of the main panel
        '
        MainPanel.Dock = DockStyle.Right
        MainPanel.Size = New Size(MainPanel.Width * 0.5, MainPanel.Height)

        Dim btn As New Button
        btn.Size = New Size(10, 50)
        btn.Location = New Point(MainPanel.Location.X - btn.Width, MainPanel.Location.Y)
        Me.Controls.Add(btn)


        tmpPanel = New Panel
        With tmpPanel
            .Size = New Size(10, MainPanel.Height)
            .Location = New Point(MainPanel.Location.X - .Width - 5, MainPanel.Location.Y)
            .Name = "Panel2"
            .Dock = DockStyle.Fill
            .BackColor = Color.Brown
        End With

        ' THIS SPLITTER IS NOT IN THE RIGHT PLACE. Must be between brown and gray panel
        '
        tmpSplitter = New Splitter
        With tmpSplitter
            .Size = New Size(5, MainPanel.Height)
            .Location = New Point(MainPanel.Location.X - .Width, MainPanel.Location.Y)
            .Name = "Split2"
            .Dock = DockStyle.Right
            .BackColor = Color.Green
            .Cursor = Cursors.VSplit
        End With

        Me.Controls.Add(tmpSplitter)
        Me.Controls.Add(tmpPanel)

    End Sub
End Class

What I have tried:

I changed the location of Splitter, but it wasn't meaningless. It can be done manually during the design phase, but it cannot be done with code at run time.