different cost for different services

[sub]

Hello everybody,
I'm going to set-up different services that are going to use the same
freeradius server and accounts.
So actually I have user X that with the same username/password can use
service A and service B connecting from different NAS; services have a
different cost to the end user.

Is it possibile to configure freeradius in such a way where, for me,
cost means a different amount of seconds?

Thanks,
sub