Gather 'round, boys and girls, there's a treat for you tonight.

I needed to dock a form in Word but couldn't find a solution.  Google showed several failed attempts.
So I sat down and beat some code into submission.

There are some caveats:

1. The form only docks to a specific edge right now (right edge).
The reason is that a toolbar changes its X/Y dimensions when docked to horizontal/vertical edges and I didn't find a way to deal with that.
Suggestions are more than welcome.

2. I am really not a VBA guru.  If you find a way to clean or streamline this code, please post.

Here's the beef:

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Option Explicit

Public Declare Function GetWindowRect Lib "user32" _
   (ByVal hwnd As Long, lpRect As RECT) As Long

Private Declare Function SetWindowPos Lib "user32" _
   (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, ByVal X As Long, ByVal Y As Long, _
    ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long

Public Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
   (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Public Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" _
   (ByVal hWndParent As Long, ByVal hwndChildAfter As Long, _
    ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Public Declare Function EnumChildWindows Lib "user32" _
   (ByVal hWndParent As Long, ByVal lpEnumFunc As Long, ByVal lParam As Long) As Long

Public Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
   (ByVal hwnd As Long, ByVal nIndex As Long) As Long

Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
   (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long

Public Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" _
   (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

Public Declare Function GetClassName Lib "user32" Alias "GetClassNameA" _
   (ByVal hwnd As Long, ByVal lpClassName As String, ByVal nMaxCount As Long) As Long

Public Declare Function SetParent Lib "user32" _
   (ByVal hWndChild As Long, ByVal hWndNewParent As Long) As Long

Public Type RECT
   Left As Long
   Top As Long
   Right As Long
   Bottom As Long
End Type

Public Const GWL_STYLE As Long = (-16)
Public Const WS_DLGFRAME As Long = &H400000
Public Const WS_VISIBLE As Long = &H10000000
Public Const WS_CHILD As Long = &H40000000

Public Const SWP_NOSIZE = &H1
Public Const SWP_NOMOVE = &H2
Public Const SWP_NOZORDER = &H4
Public Const SWP_NOREDRAW = &H8
Public Const SWP_NOACTIVATE = &H10
Public Const SWP_FRAMECHANGED = &H20        '  The frame changed: send WM_NCCALCSIZE
Public Const SWP_SHOWWINDOW = &H40
Public Const SWP_HIDEWINDOW = &H80
Public Const SWP_NOCOPYBITS = &H100
Public Const SWP_NOOWNERZORDER = &H200      '  Don't do owner Z ordering

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Private cb As CommandBar
Private ctl As CommandBarControl
Private BarHandle As Long

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Function EnumChildProc(ByVal hwnd As Long, ByVal lParam As Long) As Long
   Dim length As Long
   Dim text As String
   
   EnumChildProc = 1
   text = String$(256, 0)
   length = GetClassName(hwnd, text, 256)
   If (length <> 0) And (Left$(text, length) = "MsoCommandBar") Then
       length = GetWindowText(hwnd, text, 256)
       If (length <> 0) And (Left$(text, length) = "Docker") Then
           BarHandle = hwnd
           EnumChildProc = 0
       End If
   End If
End Function

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Sub DockForm()
   Set ctl = CommandBars.FindControl(Tag:="Filler")
   If ctl Is Nothing Then
       Set cb = CommandBars.Add(Name:="Docker", Position:=msoBarRight, Temporary:=True)
       Set ctl = cb.Controls.Add(Type:=msoControlButton, Temporary:=True)
       With cb
           .Visible = True
           .Enabled = True
           .Protection = msoBarNoCustomize Or msoBarNoResize & msoBarNoMove
       End With
       With ctl
           .Tag = "Filler"
           .Enabled = False
           .Visible = True
       End With
   Else
       Set cb = CommandBars("Docker")
   End If

   MyForm.Show vbModeless
   Dim FormHandle As Long
   FormHandle = FindWindow("ThunderDFrame", MyForm.Caption)

   Dim AppHandle As Long
   AppHandle = FindWindow("OpusApp", _
                          ActiveWindow.Caption & " - " & Application.Caption)
   If AppHandle = 0 Then
       AppHandle = FindWindow("OpusApp", vbNullString)
   End If

   EnumChildWindows AppHandle, AddressOf EnumChildProc, 0&

   Dim height As Long
   height = Application.PointsToPixels(MyForm.InsideWidth, True)
   
   SetWindowLong FormHandle, GWL_STYLE, WS_CHILD Or WS_VISIBLE Or WS_DLGFRAME
   SetParent FormHandle, BarHandle
   SetWindowPos FormHandle, 0, 0, 0, 0, 0, SWP_NOSIZE Or SWP_NOZORDER Or SWP_FRAMECHANGED
   
   ctl.height = height
   ctl.Width = Application.PointsToPixels(MyForm.InsideHeight, True)

   Dim rct As RECT
   GetWindowRect BarHandle, rct
   SetWindowPos FormHandle, 0, 0, Application.PixelsToPoints(rct.Bottom - rct.Top - height), _
                0, 0, SWP_NOSIZE Or SWP_NOZORDER Or SWP_FRAMECHANGED
   
End Sub

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Sub Cleanup()
   MyForm.Hide
   If Not ctl Is Nothing Then
       ctl.Delete Temporary:úlse
   End If
   If Not cb Is Nothing Then
       cb.Delete
   End If
End Sub

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Best wishes,
Alex.