Dear Mr Zanis,
 
thank you very much for your help about how to change LANDUSE, but I think that what you recommended me concerns the alter of landuse over the ENTIRE region of simulation, while my problem is how to change the landuse over some certain gridcells of the entire region. 
 
 Any suggestions would be very precious and helpful.
 
Thank you in advance,  
 
Christina Oikonomou.