Hi Florencia,
You have at least three different options to do this.
1. Try using Monitoring application in CMC which is a out of box solution. Using this you can monitor specific server and its metrics using probes and watches. You can refer below blogs for more details
SAP BusinessObjects 4.0 Monitoring Configuration - Part(1)
SAP BusinessObjects 4.0 Monitoring Configuration - Part(2)
2. You have the provision to integrate 3rd party monitoring solutions such as SAP Solution manager or IBM Tivoli. These tools will be making use of the BusinessObjects server process IDs to get the metrics of each server.
http://wiki.sdn.sap.com/wiki/display/BOBJ/Enterprise+Monitoring+and+BusinessObjects+Enterprise+XI
To understand the individual executables for each BusinessObjects server refer this
BusinessObjects Servers monitoring and their executables path
3. Using custom SDK code to develop your required monitoring screen
http://www.sdn.sap.com/irj/boc/samples (Server management section)
Regards
Mani