Hi Rahma,
you need to create one specific dataset with all measures you need and pass them in the text widget..
Besides, there is the possibility to apply some functions as sum or average, but it is not possible to create computed fields (cause operations like +,+,/,* are not available).
https://www.knowage-suite.com/qa/?qa=blob&qa_blobid=9135060004450333488
Regards,
Nunzia