How to request UAC in fsi and fsharp script

I have a script:

open System
open System.IO

let fileSize path =
    try
        Some((new FileInfo(path)).Length)
    with
    | e ->
        printfn "%A" e
        None

let dirSize dir =
    Directory.GetFiles(dir,"*",SearchOption.AllDirectories)
    |> Array.map fileSize
    |> Array.map (Option.defaultValue 0L)
    |> Array.reduce (+)

dirSize """C:\Users\xxx\Documents""";;

I get a System.UnauthorizedAccessException running it.
I try to run cmd or fsi as administrator ,but either worked.
I find a solution used in fsharp program by using Manifest file.
But the --win32manifest option can't be used in fsi(it's an option of fsc).
error FS0243: Unrecognized option: '--win32manifest'.

Is there any solution to request UAC in script?
(I know how to fix the script above by replacing the GetFiles method to catch the exception)