Isto aqui deve resolver
Public Enum OpcaoOnTop
OnOnTop = 1
OffOnTop = 2
End Enum
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
Private Const conHwndTopmost = -1
Private Const conHwndNoTopmost = -2
Private Const SWP_NOMOVE = 2
Private Const SWP_NOSIZE = 1
Private Const FLAGS = SWP_NOMOVE Or SWP_NOSIZE
'Para usá-la use a função abaixo:
Public Sub FormOnTop(gForm As Form, Opcao As OpcaoOnTop)
Select Case Opcao
Case 1
SetWindowPos gForm.hwnd, -1, 0, 0, 0, 0, FLAGS
Case 2
SetWindowPos gForm.hwnd, -2, 0, 0, 0, 0, FLAGS
End Select
End Sub
FormOnTop Form1, OffOnTop