Salut Pierre,

C'est la fonction API SetWindowPos.
Dans un module:
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 Const SWP_NOSIZE = &H1
Public Const SWP_NOMOVE = &H2
Public Const FLAGS As Long = SWP_NOMOVE Or SWP_NOSIZE
Public Const HWND_TOPMOST = -1
Public Const HWND_NOTOPMOST = -2

Dans ta form:
SetWindowPos Me.hwnd, HWND_TOPMOST, 0, 0, 0, 0, FLAGS