select 
   cast([колонка с нумерацией этих предметов] as varchar) + '-' + 
      isnull(cast(lead([колонка с нумерацией этих предметов])over(partition by предмет order by [колонка с нумерацией этих предметов]) as varchar),'') 

SELECT CHook, CRowASC FROM SomeTable WHERE Box = 1
union all
SELECT m.CHook,m.CRowASC FROM SomeTable m JOIN SomeTable t on (m.CHook = t.CHook) AND (m.CRowASC = t.CRowASC+1) and t.Box = 1 

select * from 
  (SELECT CHook, CRowASC FROM SomeTable WHERE Box = 1
  union all
  SELECT m.CHook,m.CRowASC FROM SomeTable m JOIN SomeTable t on (m.CHook = t.CHook) AND (m.CRowASC = t.CRowASC+1) and t.Box = 1) t
order by 1 

with t as
(
 select
  Box, CHook, CRowASC,
  lead(CRowASC) over (partition by CHook order by CRowASC) as CRowASC__next
 from
  SomeTable
)
select
 t.CHook, a.CRowASC
from
 t cross apply
 (values (t.CRowASC), (t.CRowASC__next)) a(CRowASC)
where t.Box = 1 and a.CRowASC is not null
;