Dear Vishwas ,
you can create service contract order with 5 line items or 1 line items with quantity as 1 month, based on your scenario through billing plan you have to give start date and end date .here you have write rotinue for base price condition in condition calculation rule , based on from and to date(year by year) total values in DMS /12 and this price will copy every month to your sales order from DMS to Rotinue through interface.
Regards,