Home Directory change to My Documents

[Guest]

I am trying to copy data from older legacy users that were setup with a home directory to the new standard below:

Old: \\Servername\Username
New: \\Servername\Username\My Documents

Also, the new location will not be hard coded in the user's profile, but instead will be using a Group Policy to redirect the \\Servername\%username%\MyDocuments AND grant only the user permission. So my problem is I have to have the user with just domain user right move the files while they are logged in. I have tried using Robocopy and failed. It seems simple enough, but any help would be appreciated