>How can I duplicate the following code using the seek command:
>

> SCAN
> SELECT Invoice
> LOCATE FOR in_code = lnCustCode
>   DO WHILE FOUND()
>     do some code
>     CONTINUE
>   ENDDO
> SELECT sometable
> ENDSCAN
>

>
>The is extremely slow as this codes is already in another loop and therefore a locate for the whole table is execute each time.
>
>Thanks in advance.
Made index by In_Code in Invoice table, then try

SELECT Invoice
SET ORDER TO InCodeTagName
SELECT sometable
SCAN
  SELECT Invoice
  SEEK lnCustCode
  SCAN WHILE In_Code = m.lnCustCode
       do some code
       SELECT Invoice && Not neccessary but I prefere to put it
  ENDSCAN
  SELECT sometable
ENDSCAN