Backup software question?

I have a general question, im looking for a backup program that will backup specific files to the network and the tricky part is i want it to back up automatically at a givin time i choose and have it back up to one file all the time. In other words i dont want it to make a new back up fill everytime, differentially or incrementally. I would like it to decide which files have been added or changed and back it up to the same file every time. Is this possible. Does anyone know of a program that does this

Im currently using the NTI backup program but it makes a new file every time it backs up.

 

I think this might fit the bill: Karen's Replicator http://majorgeeks.com/Karens_Replicator_d3917.html