How to add particluar column dynamically to an internal table

Question

Hi
How can I add particluar column(s) to an internal table dynamically and then display in an alv.
for eg:
There are 5 columns and the 4th column is the <b>period (1 to 12)</b> that has been declared as select-options in the selection screen.
col1 = bukrs
col2 = lifnr
col3 = akont
<b>col4 = period</b>
col5 = waers
so my question is
if period is in the range from 1 to 3 then the internal table should be
bukrs  lifnr  akont   <b>period1   period2  period 3</b>  waers. 
likewise if the period is in the range from 1 to n then internal table should be
Bukrs  lifnr   akont   <b> period1   period2   period3   period4 .....  periodn  </b> waers.
Thanks

Answer 1

Hi,
First create a global field catalog with all 12 periods ie period1, period2, ....period12.
Once you have fieldcatalog with all 12 periods
Then use this code arrive the dynamic field in the fieldcatalog
data : begin of i_period occurs 0.
data : period type i.
data : end of i_period.
data : v_no type i value 1.
do.
  i_period-period = v_no.
  v_no = v_no +1.
  if v_no eq 12.
     exit.
  endif.
enddo.
" Here arrive the periods that are not belong to selection option period
delete i_period where period in s_period.
data : v_fldname like dd03l-fieldname.
loop at i_period.
  concatenate 'PERIOD' i_period-period into v_fldname.
  condense v_fldname no-gaps.
  read table i_fieldcat with key fieldname = v_fldname.
  if sy-subrc eq 0.
     delete i_fieldcat index sy-tabix.
  endif.
endloop.
After this loop your field catalog contains only valid period that equal to selection option period
aRs