You need to use a SCAN or a if loop to skip through your target table. Set a relation from your target table to the source table. Make sure the relationship mimics the primekey on your source table. You can set a primekey on the target table but I usually do not do this for small tables.

select target
scan
if not eof("source")
replace target. , .... with source. ,...
endif
endscan


Your target table would be the table your are making the updates to.