Sub Main()
Dim FreeString As String
    MyFreeSpace = GetFreeSpace("C")
    FreeString = Format(MyFreeSpace, "#,###")
    MsgBox "Free space on C is " & FreeString
End Sub

Private Function GetFreeSpace(ByVal strDriveLetter As String) As Long
    Dim fso As Scripting.FileSystemObject
    Dim dr As Scripting.Drive
    
    Set fso = New Scripting.FileSystemObject
    
    GetFreeSpace = fso.GetDrive(strDriveLetter).FreeSpace
    
    Set fso = Nothing
    
End Function