If this is just a string that you are retrieving from a table, you could put a placeholder in the string, then use STRTRAN to replace the placeholder with the alias.

lcStr = 'where ALIAS.CODE # ALIAS.PARENTCODE .OR. ALIAS.PCOFLAG = "P"'

>Hi everyone,
>
>I have some expression, which is either filter() or for() or combination of both. I'd like to insert Alias Lnd1 before each field, which may be in this expression. Example:
>

lcStr=where CODE#PARENTCODE.OR.PCOFLAG="P"

>
>I need to convert it to 'where lnd1.code#lnd1.parentcode OR lnd1.PCOFLAG="P"'
>
>I was thinking about checking this string against each field and do simple strtran, but it would not work, since I have fieldnames, which are part of other field names.
>
>Could you please help me?
>
>Thanks in advance.