How to create a subpanel as a child window?

[qwert]

After reading about $WS_EX_MDICHILD, I thought this would be simple. "Create a child window included in its parent window." it says ... but nothing I've tried will work. The PNG shows what I was expecting. This is my script, so far:

#include <GUIConstantsEx.au3>
#include <GuiRichEdit.au3>
#include <WindowsConstants.au3>
#Include <GuiScrollBars.au3>
#include <ScrollBarConstants.au3>
Opt("GUIOnEventMode", 1)
$Form = GUICreate("Test", 600, 300, -1, -1,-1 ,BitOR($WS_EX_WINDOWEDGE, $WS_EX_TOPMOST))
GUISetOnEvent($GUI_EVENT_CLOSE, "Terminate")
GUICtrlCreateLabel("Text Field", 20, 20)
$rich1 = _GUICtrlRichEdit_Create($Form, "", 20, 40, 200, 200, BitOR($ES_WANTRETURN, $ES_MULTILINE, $WS_VSCROLL))
GUICtrlSetState(-1, $GUI_DROPACCEPTED)
_GUIScrollBars_ShowScrollBar($rich1, $SB_VERT, True)
GUISetState(@SW_SHOW)
$SubForm = GUICreate("Side Panel", 300, 240, 240, 40, $WS_CHILD ,BitOR($WS_EX_WINDOWEDGE, $WS_EX_TOPMOST, $WS_EX_MDICHILD), $Form)
GUICtrlCreateLabel("Second Text Field", 300, 20)
$rich2 = _GUICtrlRichEdit_Create($SubForm, "", 20, 40, 200, 200, BitOR($ES_WANTRETURN, $ES_MULTILINE, $WS_VSCROLL))
GUICtrlSetState(-1, $GUI_DROPACCEPTED)
_GUIScrollBars_ShowScrollBar($rich2, $SB_VERT, True)
GUISetState(@SW_SHOW)
While 1
Sleep(50)
WEnd
Func Terminate()
    _GUICtrlRichEdit_Destroy($rich1)
    _GUICtrlRichEdit_Destroy($rich2)
    Exit
EndFunc

If I'm completely misunderstanding, please let me know. My end objective is to have a 3-tap panel as a sub-window, which eventually might be able to be "detachable" (free-floating).

Thanks for any assistance.

[JohnOne]

$SubForm = GUICreate("Side Panel", 300, 240, 240, 40, -1 ,BitOR($WS_EX_WINDOWEDGE, $WS_EX_TOPMOST, $WS_EX_MDICHILD), $Form)

I don't know why.

[qwert]

Wow. That works! ... and I probably would never have thought to try it.

Thanks very much.

[martin]

WS_CHILD and WS_EX_MDICHILD don't go together so

$SubForm = GUICreate("Side Panel", 300, 240, 240, 40, $WS_CHILD ,BitOR($WS_EX_WINDOWEDGE,$WS_EX_TOPMOST), $Form)

or

$SubForm = GUICreate("Side Panel", 300, 240, 240, 40, $WS_CHILD ,-1, $Form)

should work.

[qwert]

$SubForm = GUICreate("Side Panel", 300, 240, 240, 40, -1 ,BitOR($WS_EX_WINDOWEDGE, $WS_EX_TOPMOST, $WS_EX_MDICHILD), $Form)

I don't know why.

martin, just as a clarification: I tried both of your suggestions, but neither produced the overlaid window effect that JohnOne's suggestion (using -1) did. I don't have time to delve into why, but thanks for the response.