Seq     Ticker       Qty
===     ======       ===
1       msft         50
2       msft         75
3       msft         110

Seq     Ticker       Qty
===     ======       ===
1       msft         50
2       msft         50

Seq     Ticker       Qty
===     ======       ===
2       msft         25
3       msft         110

declare @param int=100;

select a.seq
      ,a.ticker
      ,case when sum(b.qty)>@param then @param-(sum(b.qty)-a.qty) else a.qty end as qty
  into #temptable
  from table1 as a
       inner join table1 as b
               on b.ticker=a.ticker
              and b.seq<=a.seq
 group by a.ticker
         ,a.seq
         ,a.qty
 having sum(b.qty)-a.qty<@param
;

delete from table1
 where exists (select 1
                 from #temptable
                where #temptable.ticker=table1.ticker
                  and #temptable.seq=table1.seq
                  and #temptable.qty=table1.qty
              )
;

update a
   set a.qty=a.qty-b.qty
  from table1 as a
       inner join #temptable as b
               on b.ticker=a.ticker
              and b.seq=a.seq
;

update a
   set a.qty=a.qty+b.qty
  from table2 as a
       inner join #temptable as b
               on b.ticker=a.ticker
              and b.seq=a.seq
;

insert into table2
   select *
     from #temptable as a
    where not exists (select 1
                        from table2 as b
                       where b.ticker=a.ticker
                         and b.seq=a.seq
                     )
;

drop table #temptable;