We are in the process of creating tiers for our support offerings.     There will be three tiers of support available - 2 paid and 1 free.     The paid tiers will be purchased in allotted hours. 

I need to figure out how to a) work in the out of the box SLA, Contracts and Support Plans in with time-tracking.   Ideally, this would look like a new field on the Support Plan/Contract that would like the number of hours purchased along with the number of hours used and the number of hours left, the latter two both calculated.  

The hours would need to be available from the account screen and also the ticket screen so first level agents could see  what level of service the customer has and if it's paid, the number of hours left that can be used.

Any ideas on how to best set this up?    Can someone from zoho perhaps help with some custom deluge code that could total number of hours used on the current plan and display that someone for the agents to see? 

Any help, advise or suggestions are very much welcomed.