I have created a custom activity to Update any FIM 2010 R2 Portal Resource.
Please follow the link below
http://gallery.technet.microsoft.com/FIM-2010-R2-Custom-bd3a9a32
you can download the DLL and use it without any warranty.
It runs a powershell command in the background to update the any portal resource.
It takes the ObjectID (ResourceID) for the resource to be updated, the attribute you want to update and the value for the attribute.
Please fele free to use and comment.
Thanks