fCdlg.Owner = Me
    fCdlg.DialogType = eCDLFile
    With fCdlg.cdlg
        .DialogTitle = "Choose a File to Open"
        .Filter = "Text Files (*.TXT)|*.TXT|All Files (*.*)|*.*"
        .FilterIndex = 1
        .Flags = cdlOFNFileMustExist Or cdlOFNPathMustExist
        .ShowOpen
    End With

And by the way, remember to include Unload fCDlg when your application ends, otherwise the invisible form will stop your project from terminating.

Whilst this works just fine, the problem with it is we must hardcode the size and offsets from the left and top for each of the Common Dialogs. Can you be sure the dialog is the same size on all systems? What if the user has larger fonts set up in the title bar? Even the above code is not complete. For example, on a color dialog, you can set a flag saying whether the whole dialog appears including colour customisation, or whether just the standard colours appear. Clearly, the dialog has a different size depending on the setting of this flag, but I haven't coded it in.

What we really want to have is an event which occurs when the dialog opens, saying what size its going to be and requesting a Left and Top position. This is possible, but to do it you need to delve into Common Dialog hooks and subclassing. And to do this, you need to create a Common Dialog box using the API rather than using the VB one.

The Hard Way
The real method to achieve a centred Common Dialog is to utilise a Hook function. When Common Dialogs are created via the COMDLG32.DLL API, each dialog provides a method to provide the address of a function in your code. The Common Dialog can then call this function within your code to notify your application of any actions you may wish to respond to.

Taking a sample of the File Open Common Dialog, here is how it works. To create a File Open box through the API, you fill in an OPENFILENAME structure and then call the GetOpenFileName API function exposed by COMDLG32.DLL with the structure as a parameter. One of the fields of the OPENFILENAME structure is lpfnHook. This takes a long pointer to a function, which must be constructed in accordance with the function COMDLG32 expects to call. In VB, you can pass a pointer to a function by using AddressOf, provided the function itself lives within a module (- most irritatingly!).

So, to take advantage of a hook, you do the following:

Set Up a Hook Function
The code for the hook function in VB is as follows:

Public Sub CentreDialog(ByVal hDlg As Long, ByRef oCentreTo As Object)
Dim lHwnd As Long
Dim tWR As RECT, tDR As RECT
Dim tp As POINTAPI
Dim lHwndCentreTo As Long
Dim lL As Long
Dim lT As Long
Dim lR As Long

    ' If we're showing a file dialog, then the rectangle is the
    ' parent of the dialog itself:
    If (m_bFileDialog) Then
        lHwnd = GetParent(hDlg)
    Else
        lHwnd = hDlg
    End If
    GetWindowRect lHwnd, tDR
    Debug.Print tDR.Right - tDR.Left, tDR.Bottom - tDR.Top
   
    On Error Resume Next
    lHwndCentreTo = oCentreTo.hwnd
    If (Err.Number = 0) Then
        GetWindowRect lHwndCentreTo, tWR
    Else
    ' Assume the screen object:
    lR = SystemParametersInfo(SPI_GETWORKAREA, 0, tWR, 0)
    If (lR = 0) Then
        ' Call failed - just use standard screen:
        tWR.Left = 0
        tWR.Top = 0
        tWR.Right = Screen.Width \ Screen.TwipsPerPixelX
        tWR.Bottom = Screen.Height \ Screen.TwipsPerPixelY
    End If
    End If
    On Error GoTo 0
    If (tWR.Right > 0) And (tWR.Bottom > 0) Then
        lL = tWR.Left + (((tWR.Right - tWR.Left) - (tDR.Right - tDR.Left)) \ 2)
        lT = tWR.Top + (((tWR.Bottom - tWR.Top) - (tDR.Bottom - tDR.Top)) \ 2)
        Debug.Print tDR.Right - tDR.Left, tDR.Bottom - tDR.Top
        MoveWindow lHwnd, lL, lT, (tDR.Right - tDR.Left), (tDR.Bottom - tDR.Top), 1
    End If
End Sub