Utilizzi la funzione FileLen:
codice:
Const Cartella = "C:\Documenti\"
Const FileDest = "C:\Documenti\Lista.txt"
Const NumSpazi = 70
Dim FileName As String
Dim ContFile As Long
Dim StrTemp As String


FileName = Dir(Cartella, vbNormal + vbSystem + vbHidden + vbReadOnly)
Open FileDest For Output As #1
Print #1, "* File in "; Cartella; " :"; vbCrLf
  Do Until Len(FileName) = 0
    StrTemp = CStr(FileLen(Cartella & FileName))
    StrTemp = Space(NumSpazi - Len(StrTemp) - Len(FileName)) & StrTemp & " byte"
    
    Print #1, FileName; StrTemp
    FileName = Dir
    ContFile = ContFile + 1
  Loop
  Print #1, vbCrLf; "* File trovati : " & CStr(ContFile); "."
Close #1