>>So some records have an ID that already exists. Other records have unique ID.
>>I want to run this table through a PRG and add a suffix '1', or '2', or '3' (depending on each duplicate record). So that the above table would look like this:

How about something along the lines of

select id_field,count(*) as cnt from mytable group by 1 order by 1 having cnt>1 into cursor c_fixme
SCAN
  licounter=0
  update mytable set id_field = rtrim(id_field)+mysuffix() where id_field=c_fixme.cid_field 
endscan

function mysuffix()
licounter=m.licounter+1
return transform(m.licounter)