NTReplaceFile

Public Const MOVEFILE_DELAY_UNTIL_REBOOT = &H4
Public Const MOVEFILE_REPLACE_EXISTING = &H1
Public Const MOVEFILE_COPY_ALLOWED = &H2

Public Declare Function MoveFileEx Lib "kernel32" _
Alias "MoveFileExA" (ByVal lpExistingFileName As String, _
ByVal lpNewFileName As String, ByVal dwFlags As Long) As Long

Public Sub Main()
Dim Hold As Variant, Hold2 As String, Hold3 As String, X As Long
Dim Silent As Boolean
Hold = Command
If Hold = "" Then Goto ErrH 'No Command switches passed
If UCase(Left(Hold, 2)) = "-S" Then
Silent = True 'Silent install
Hold = Right(Hold, (Len(Hold)) - 3)
End If
'Parse the switches

Hold2 = Trim(Left(Hold, InStr(Hold, " ")))
Hold3 = Trim(Right(Hold, (Len(Hold)) - (InStr(Hold, " "))))
X = MoveFileEx(Hold2, Hold3, MOVEFILE_DELAY_UNTIL_REBOOT)
If Silent And X = 1 Then Exit Sub
If X = 1 Then
Msg= "Success, File " & Hold2 & " & _
"will be renamed To " & Hold3 & " at Next reboot" _
, vbApplicationModal, "File Replacement"
Else
Msg = "Failure, Check syntax. Example, " & _
"-S C:\Winnt\system32\YourFile.dll{Space}" & _
"C:\Winnt\system32\YourFile.OLD" & vbCrLf & _
"-S switch used For silent installations, " & _
"dialog only raised on failure"
'Msg = MsgBox

End If
Exit Sub
ErrH:
Msg = "Failure, Check syntax. Example, -S " & _
"C:\Winnt\system32\YourFile.dll{Space}" & _
"C:\Winnt\system32\YourFile.OLD" & _
vbCrLf & "-S switch used For silent installations," & _
"dialog only raised on failure"
'Msg = MsgBox

End Sub
Inputs: -S for Silent installs [Optional] Sourcefile, DestFile

Returns: 1 on success

Assumes:
typical command line where no dialog is raised would look like
this to replace a system dll:
Replace.exe -S C:\winnt\Src.dll C:\Winnt\Src.old
Replace.exe -S C:\temp\Src.dll C:\Winnt\Src.dll

Which can be run from a batch file etc..