I am trying to use the seek command to do a lookup in a zipcode table. I have two tables

mytable zip c(5) and county c(15)
zipcodes zip c(5) and county c(15) index tag zip_t

my code looks like this

use mytable in 0
use zipcodes in 0 order zip_t
sele mytable
scan
hld_cnty = ' '
scatter memvar
sele zipcode
seek(m.zip)
if found() then
hld_cnty = zipcode.county
sele mytable
replace mytable.county with hld_cnty
end if
endscan

However the seek never finds any matching records?????