SLA based on Time of Day

Hi Everyone. I am new to ME ServiceDesk only had it for 3 days, so I am muddling my way through. I have clients that have different SLA's based on the time of day the request is made. I would like to be able to setup up SLA's within ME to reflect this. I understand from what I have seen that this isn't too easy if at all possible. I have been playing with Priorities, but once again there is no way of using those based on time, unless of course I name the priority in that way i.e. Priority = [clientname - 08:00-17:00]. Does anyone have any other ideas? Also when setting up sites I see that if you change SLA, Technicians, support groups or business rules to custom it changes all of them and not individually. Is that normal, or just my system.

This is what I am doing so far to achieve SLA management for clients that aren't standard. The clients that have standard SLA are under common settings.

Create Account

Create Site - Move all radio buttons to Custom.

Associate Technicians to Site

Create Support Group (have to do this for each site) this is a pain, not sure why my support groups aren't available to me.

Create priorities

Create business rules

Create SLA (when I can work out my time issue)

Is there an easier way?

Many thanks for reading this long winded message, and any help very gratefully received.

Regards

Lionel