Yes. I believe the following is what you are after. The 2 tables do not have to be open.

update table1 set table1.cvar1 = 'aaa' where table1.key in (select table2.key from table2 where table2.field1 between 100 and 200)

>Hi,
>
>Does something exists like a SQL-Replace command? Something like:
>
>REPLACE Table1.cvar1 WITH 'aaa' ;
> FROM Table1,Table2 ;
> WHERE table2.Key = table1.key ;
>AND Table2.Field1 BETWEEN 100 AND 200
>
>Table1 and Table2 whould be opened on the fly if they werent't yet.
>
>I can dream, no?
>
>Thank you.
>
>Alex