How can I tell if a file is in use?

I am working on a pretty cool little project to add to my existing application that will check the web for updates to my program. If files on the client are older than any of the files on the web server it will allow them to automatically update them. The only problem is...

If it is copying a file that is in use (like a system dll) then I can not copy it using normal methods. I will have to use the registry method. That is fine. What I need though is to know when a file is in use so I can invoke the correct method of updating it.

TIA,
Richard

Try this:

Code:

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Private Declare Function lOpen Lib "kernel32" Alias "_lopen" (ByVal lpPathName As String, ByVal iReadWrite As Long) As Long
Private Declare Function lClose Lib "kernel32" Alias "_lclose" (ByVal hFile As Long) As Long


Function IsFileAlreadyOpen(FileName As String) As Boolean

 Dim hFile As Long
 Dim lastErr As Long

 ' Initialize file handle And Error variable.
 hFile = -1
 lastErr = 0

 ' Open for for read And exclusive sharing.
 hFile = lOpen(FileName, &H10)

 ' If we couldn't Open the file, Get the last error.
 If hFile = -1 Then
    lastErr = Err.LastDllError
    Else
    ' Make sure we Close the file On success.
    lClose (hFile)
 End If

 ' Check for sharing violation error.
 sFileAlreadyOpen = (hFile = 1) And (lastErr = 32)

End Function

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Cool, thanks for the help. I will check it out right now.