Multiple SLA's against an Entitlement

Hi Guys,

Is it possible to customise CRM to add multiple SLA's against an Entitlement?

Our issue is:

Depending on the Priority of the Case, the Work Hours are different. 

The only way I can think of getting around this is by having multiple SLA's against the Entitlement.

Multi-Entitlement doesn't work as the Total Terms will be at the Account Level. And multiple Entitlements doesn't roll-up the Total Terms on the Entitlement Level.

Cheers,