WSH: set write permissions in a directory

I'm using Windows Scripting Host (WSH), called from an ASP file, to create new directories on the server when a visitor signs up for a service:

CODE:
<%
Dim objShell
Set objShell = CreateObject( "Scripting.FileSystemObject" )
objShell.CreateFolder "F:\Webfolder\" & username
objShell.CreateFolder "F:\Webfolder\" & username & "\images"
Set objShell = Nothing
%>

This creates a new folder with the user's name (alpha numeric only permitted) and an "images" subdirectory.

However, these are created as read-only, by default; I want to make the folders writeable as well.

I can't find a WSH method to alter these permissions that I can get to work.

Any suggestions?

Thanks