Do they need to be contiguous? If not, just list the file twice in the next step.
I don't think File-Aid CAN write twice. If any function can do it, it will be the USER function.
If you have sort available, you could use:
SORT FIELDS=COPY
INCLUDE COND=(5,4,CH,EQ,C'SEG1')
OUTFIL OUTREC=(17,10,/,17,10)
That's if I remember my File-Aid format.
If it's a variable length file, you need to add 4 to all the positions, plus tell sort to make it fixed length:
SORT FIELDS=COPY
INCLUDE COND=(9,4,CH,EQ,C'SEG1')
OUTFIL CONVERT,OUTREC=(21,10,/,21,10)