creon

Thanks for your replies. yeah you're right the j++ is in the if

j=0
for i=0,20 do begin
if (data.field08[i]='V') then begin
dataV.time[j]=data.field10[i]
dataV.object[j]=data.field07[i]
dataV.count[j]=data.field09[i]
dataV.filter[j]=data.field08[i]
j++
endif
endfor

Maybe i should explain better. i have some observation data with
time, object, filter and count in each column. the structure called
data carries those.There are three diffrent filters U,B, and V. now i
want to pick the data in V filter and write it to the structure dataV.
i am new to idl programming so that loop is what i could find to do
this task. is there any other way to do this? or am i doing something
wrong?