How to resize a parent form and panel to fit a child window

I use the code below to start a cmd.exe windows and move it into a panel after execution. At this moment, the child window is resized to fit into Panel1 on my Form1. I would like it to be the other way around: my Form1 (and thus Panel1) should resize to fit the size of the child window, so no matter what the size of the default cmd.exe window is on the local computer. Does anybody know how I should do that? Thanks for any help in advance!

Kind regards, Eric

Imports System.Runtime.InteropServices
Public Class Form1
    Private WithEvents Tmr As New Timer With {.Interval = 100}
    Private Const HWND_BOTTOM As Integer = &H1
    Private WithEvents proc As New Process
    <DllImport("user32.dll", EntryPoint:="SetParent")>
    Private Shared Function SetParent(ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As IntPtr
    End Function
    <DllImport("user32.dll", EntryPoint:="SetWindowPos")>
    Private Shared Function SetWindowPos(ByVal hWnd As IntPtr, ByVal hWndInsertAfter As IntPtr, ByVal X As Integer, ByVal Y As Integer, ByVal cx As Integer, ByVal cy As Integer, ByVal uFlags As UInteger) As <MarshalAs(UnmanagedType.Bool)> Boolean
    End Function
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Text = "My title"
        proc.EnableRaisingEvents = True
        proc.StartInfo.FileName = "cmd"
        proc.Start()
        Tmr.Start()
    End Sub
    Private Sub Tmr_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Tmr.Tick
        If SetParent(proc.MainWindowHandle, Panel1.Handle) <> IntPtr.Zero Then
            Tmr.Stop()
            SetWindowPos(proc.MainWindowHandle, New IntPtr(HWND_BOTTOM), 0, 0, Panel1.ClientSize.Width, Panel1.ClientSize.Height, 0)
        End If
    End Sub
    Private Sub Proc_Exited(ByVal sender As Object, ByVal e As System.EventArgs) Handles proc.Exited
        Invoke(Sub() Close())
    End Sub
End Class

As suggested by @Jimi, I used DwmGetWindowAttribute to retrieve the size of the child, before moving it into the panel. Afterwards I use ShowWindow to maximize it, to get rid of the borders. The changed code can be found in a different post of mine.