Use values for scripts from multiple index in elasticsearch

Question

Is there a way to write a script that can read values from multiple indexes and produce results in Elasticsearch?

For eg:

curl -XGET 'localhost:9200/index1,index2/_search?pretty' -d '
{
   "script_fields" : {
      "test1" : {
         "script" : {
            "inline":"my_var1 + my_var2",
            "params":{
               "my_var1":"value from index1"
               "my_var2":"value from index2"
     }
   }
  }
}'

Say I need value from index1 and index2 be added and displayed as test. Can anyone suggest a way for achieving this?