Hi all,

I have a vb program that opens a file(.btw) if the input matches the .btw file name. How do i prevent from opening another .btw file via input if there's already one file opened? Please help me experts out there. Thanks.

I would try something like -

'Determine whether a file is already open or not
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
Private 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
        ' 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
Private Sub Form_Load()
MsgBox IsFileAlreadyOpen("c:\autoexec.bat")
End Sub