Converting multiple rows of to one conditional row.

Hello Experts.

I have an internal table like ;

  OBJECTID      DATE            CONDITION

    1                10.10.2015       'startdate'

    1                11.11.2015       'finishdate'

But I need it like;

objectid        startdate            finishdate

     1             10.10.2015       11.11.2015.

I try to use ;

loop at gt into wa

at new objectid

  if wa-condition     = 'startdate'.

        ls-startdate    = wa-date.

elseif wa-condition = 'finishdate'.

        ls-finishdate   = wa-date.

endat.

append ls into lt.

But it doen't work. How can I convert to single row?

Thank you.