Declare Auto Function GetDiskFreeSpaceEx Lib "kernel32.dll" ( _
        ByVal lpDirectoryName As String, _
        ByRef lpFreeBytesAvailableToCaller As Long, _
        ByRef lpTotalNumberOfBytes As Long, _
        ByRef lpTotalNumberOfFreeBytes As Long) As Integer
 
    Private Sub FreeSpace()
        Dim user, total, free As Long
 
        GetDiskFreeSpaceEx("C:", user, total, free)
        Debug.WriteLine("Free Space = " & free.ToString("n0"))
    End Sub