Updating Desktop Wallpaper via GPO on Windows 7 Professional - Instant effect at GPO Refresh time without needing to log off

Hello,

We have some complex requirements for Desktop Wallpaper, based on dates it must be certain wallpaper for certain groups of users, to accomplish these requirements I've used a Group Policy and Preferences within to copy files from a network share to the local hard drive (C:\Windows\Web\Wallpaper\) and set the registry entry to the new wallpaper in that location:

Control Panel\Desktop\Wallpaper

I have also tried Software\Microsoft\Windows\CurrentVersion\Policies\System\Wallpaper

Here's a nice article on someone else setting it up: http://www.grouppolicy.biz/2011/03/best-practice-using-group-policy-to-configure-desktop-wallpaper-background/

This works on Windows XP, however on Windows 7, we get the issue that currently logged on users do not receive the new wallpaper when Group Policy does a refresh.

If you check Personalization from the desktop, you can see the Desktop Background preview shows the new wallpaper, yet the desktop does not, it keeps the previous wallpaper!

Right-clicking the desktop and choosing refresh doesn't work (not that I'd want it to)

Locking and unlocking the screen does not work.

Closing explorer.exe and restarting it (often used in Windows XP days to force registry changes to explorer to take effect.

The only thing that works is to log off and back in again, however, most users login in the morning and only log off at the end of the working day.

Sadly we have a requirement to change the wallpaper during the day, sometimes to coincide with the activation of another service.

I've tried this hotfix, it won't install, so I guess it was a pre-SP1 hotfix, nor do we get the blank/black desktop issue others appear to complain about: http://support.microsoft.com/kb/977944

I don't think it's this "TranscodedWallpaper.jpg" either as that just shows the default Windows background, no matter which of our wallpapers we have applied/trying to apply/swap between. Wallpapers are usually .bmp (seemed to be required for XP) but have some .jpg as well now.

Please help, anyone else experience this issue? Have a solution? I think MS need to do another Hotfix?