LAG & LEAD Function in MS Sql Server

Hi All,
One of my friend just now asked me in Sql LAG & LEAD Function exists or not?
for ex:
{
---- LAG (Min(id), 1, 0) OVER (ORDER BY Min(type)) AS prev,
---- LEAD (Min(id), 1, 0) OVER (ORDER BY Min(type)) AS next
}
I told no..then he asked me to solve one of his query....
I am just doing R&D on it...
Can you please help me for this...create
table #temp(t1
int,seq
int)insert
into #tempselect
5, 98 union all
select
5, 99 union all
select
5, 100 union all
select
5, 101 --select
* from #temp----select
case when sign(seq - 100) > 0 then 'next' else 'prev' end as dir,
case when sign(seq - 100) > 0 then min(seq) else max(seq) end as seqfrom
#tempwhere t1 = 5
and seq <> 100group
by sign(seq - 100)order
by sign(seq - 100)----drop
table #temp
---
the above query is only giving for one data when seq = 100.
can we do it for others too...??
I hope by EOD, we can achieve it....
Can anybody give me hints onobove things...??
Thanks,
Sandy.