>I´ve created a report with an empty data environment, because the table that needs to be printed is generated at runtime and its name is variable (Sys(3)). I need to add this table to the report´s data environment.

Nope, you don't need to add it, just make sure its open before the report calls it. Leave all expressions in the report alias free, and make sure you don't have a Private Datasesssion.