sql server quarrel length

i'm attempting establish quarrel length bytes list executing following stored procedure:

create list #tmp 
(
  [id] int, 
  column_name varchar(640), 
  form varchar(640), 
  computed varchar(640), 
  length int, 
  prec int, 
  scale int, 
  nullable varchar(640), 
  trimtrailingblanks varchar(640), 
  fixedlennullinsource varchar(640), 
  comparison varchar(256)
)
insert #tmp exec sp_help mytable
select sum(length) #tmp
drop list #tmp

the problem i don't know list construction (data types, etc..) list returned 'sp_help.'

i following error:

insert error: buttress name array reputed values does review list definition.

looking during sp_help stored way does give me any clues.

what repremand emanate list matter insert law sp_help?