codice:
Dim iFile As Integer
Dim sBuffer As String
iFile = FreeFile
Open "[percorso completo del file]" For Input As #iFile
   Do Until EOF(iFile)
      Line Input #iFile, sBuffer
      If InStr(sBuffer, [Espressione da cercare]) > 0 Then
         'fai qualcosa
      End If
   Loop
Close #iFile