Sorry, there is my code:

Private Declare Function GetWindowRect Lib "user32" (ByVal hwnd As Long,
lpRect As RECT) As Long
Private Type RECT
   Left As Long
       Top As Long
       Right As Long
       Bottom As Long
End Type

Public Function centerFormOnAppWindow(frmIn As Object) As Long
   Dim w As Long, h As Long
   Dim frmLeft As Long, frmTop As Long
   Dim frmWidth As Long, frmHeight As Long
   Dim frmX As Long, frmY As Long

   Dim leftNew As Long, topNew As Long

   Dim AppW As Long, AppH As Long

   Dim AppCenterX As Long, AppCenterY As Long
   Dim dx As Long, dy As Long
   Dim dblCfnt As Double

   Dim lpRectApp As RECT, lpRectFrm As RECT
   Dim res As Long
   Dim frm As Form

   centerFormOnAppWindow = 0
   res = 0
   Set frm = Nothing
   On Error Resume Next
   Set frm = frmIn
   If frm Is Nothing Then Set frm = frmIn.Parent
   On Error GoTo 0
   If frm Is Nothing Then Exit Function
   If Not frm.Moveable Then Exit Function
   ' Access Application window parametrs
   res = GetWindowRect(Application.hWndAccessApp, lpRectApp)
   If res <> 0 Then
       With lpRectApp
           AppW = .Right - .Left
           AppH = .Bottom - .Top
       End With
       AppCenterX = AppW / 2
       AppCenterY = AppH / 2
       frmHeight = frm.WindowHeight
       frmWidth = frm.WindowWidth
       frmLeft = frm.WindowLeft
       frmTop = frm.WindowTop
       ' Form window parametrs
       res = GetWindowRect(frm.hwnd, lpRectFrm)
       If res <> 0 Then
           dblCfnt = frmWidth / (lpRectFrm.Right - lpRectFrm.Left) '
coefficient from system units (pixels?) to form units (twips?)
AppCenterX = AppCenterX * dblCfnt
           AppCenterY = AppCenterY * dblCfnt
           frmX = frmWidth / 2 + frmLeft
           frmY = frmHeight / 2 + frmTop
           dx = AppCenterX - frmX
           dy = AppCenterY - frmY
           leftNew = frmLeft + dx
           topNew = frmTop + dy
           If leftNew < 0 Then
               leftNew = 0
           End If
           If topNew < 0 Then
               topNew = 0
           End If
           If frmHeight > AppH * dblCfnt Then
               frmHeight = AppH * dblCfnt
           End If
           If frmWidth > AppW * dblCfnt Then
               frmWidth = AppW * dblCfnt
           End If
           frm.Move leftNew, topNew, frmWidth, frmHeight
       End If
   End If
   centerFormOnAppWindow = res
exit_func:
   Set frm = Nothing
   Exit Function
err_Func:
   errS = Err.Number & ": " & Err.Description & " (" & Err.Source & ")"
   Debug.Print errS
   centerFormOnAppWindow = 0
   Resume exit_func
End Function