Required library edition:
Required library file: dhtmlxgrid.js

sets user data to row

• row_id - row id. if empty then user data is set for grid (not row)
• name - name of user data block
• value - value of user data block

   //set row userdata
   mygrid.setUserData("unique_rowid","someName1","new value");
   //set global userdata
   mygrid.setUserData("","someName1","new value");

See also: getUserData