The Call Information section of the IPCC Agent Desktop screen displays call-related data for each call currently on the softphone which includes, the DNIS also.
More info on this at:
Cisco ICM Software IPCC Agent Desktop User Guide
http://www.cisco.com/univercd/cc/td/doc/product/icm/icm45/ipphone1.pdf
Also there is something called Cisco Desktop Enterprise Server Software which allows for call information (ANI, DNIS, CRA variables) to be passed with the call to the agent desktop.