[Dune] initializing parallel user data from file

[Marco Cisternino]

Good morning duners,
I would like to initialize a parallel user data vector from a grid input 
file.
The grid files (.vrt and .cel) are in PROStar format and the last column 
of the .cel file contains the values of the scalar field I want to use 
in order to initialize the user data vector.
Is there a standard way to do this?
I tried some ways but I always need to communicate a global id. Can I 
avoid this?
Thank you for your help.

Marco