reporting services - SSRS RowNumber counting a Groups in the report sequentially -

here need achieve. import purchasing system.

created ssrs report works fine. im missing 1 more step finish it. i'll try explain achieved , remains achieved.

achieved:

lineid   lnarr2

 1      751
 1      793
 1      804
 2      804
 3      804
 4      804
 1      807
 2      807
 3      807

the avobe 4 payments. payment id represented by: "lnarr2" (751, 793, 804 , 807). "lineid" counts number of lines pertaining group (purchase)

in ssrs achieved by

1. creating group, name: "lnarr2_grp" , group on: "lnarr2"
2. expression "lineid" =rownumber("lnarr2_grp")

remains achieved

following on example above. need add document id (docid). similar lineid represented follows:

docid  lineid   lnarr2

 1     1      751
 2     1      793
 3     1      804
 3     2      804
 3     3      804
 3     4      804
 4     1      807
 4     2      807
 4     3      807

the above indicates that:

• document id "1" has 1 description line
• document id "3" has 4 lines in description

question: expression "docid"? sequential count per group per example above?

thanks in advance

something this?

declare @t table (lineid int, lnarr2 int) insert @t values ( 1 ,     751 ), ( 1 ,     793 ), ( 1 ,     804 ), ( 2 ,     804 ), ( 3 ,     804 ),  (4 ,     804 ),  (1 ,     807 ),  (2 ,     807 ),  (3 ,     807 )   select  s.docid,t.lineid,t.lnarr2    @t t join (select lnarr2, row_number() on (order lnarr2) docid @t group lnarr2) s on      s.lnarr2 = t.lnarr2