Adding Folder Size to Inventory

Hi

We are in the preparatory stages of forcing a redirection of the local MyDocuments  folder for all domain clients to a nas. To get an idea

of impact on storage I want to be able to report on the amount of data which is likely to be moved.

What would be the best way to get the folder size for the MyDocuments folder for the Primary Owner of the device added to the inventory?

Thanks

Simon