There is no direct bus service between Lisbon and Caceres.
There is one direct train service per day. This is the overnight Lusitânia Comboio Hotel from Lisbon to Madrid which routes through Caceres. Cost about € 35.00 at present.
See: http://bit.ly/LisbonCaceres
The only alternative would be to tak a bus from Lisbon to Badajoz and then another from Badajoz to Caceres.
http://www.avanzabus.com have a service leaving Lisbon Oriente at 10:30 and arriving in Badajoz at 15:15 (Spanish time).
There is then a departure from Badajoz at 16:00 arriving Caceres at 17:15. Cost approximately € 40.00 at present.
