I could solve this using properties and Property Transfer

1. Add a property to the TestCase in the Custom Properties tab

2. Add a property Transfer step

   2.1 As source select the test step with the response where are the results to store

   2.2 In the drop down list of property select ResponseAsXml

   2.3 In text are of the source write the path of the xml tag like: /dataList/data

   2.4 As target select the test case where was added the custom property of (1)

   2.5 As target property select the name of the custom property added.

Thank you very much to everyone for your prompt answers :) As soon as I have better reputation I'll post some pictures.