Hours based contracts

Hours based contracts

Good morning, I offer to customer hours based contract, i've seen on forum old posts about this. I need to associate to contract hours amount (say ten in a year) and then subtract from this amount every work or intervention of technician, I also need to be advised when hours amount is near to 0. Is it possible with service desk plus?
Also which are the difference beetween Plus and PlusMSP version? I'm a MSP.
Thanks in advance.
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