>How can i use Referential Integrity between tables that belong to diferent Databases.
>
>Example:
>Database A contains Table1 and Table2
>Database B contains Table3
>
>There is a common field in Table1 and Table3
>
>How can i use an update, insertion and elimination Cascade Referential Integrity
>between them?
>
>I would apprecite any miracle.

AFAIK,Cascade Referential Integrity is limited to the scope of the DBC.
But, you can update fields in a table in one DBC with data from a field in another table in another DBC by something similar:

REPLACE A!table1.fieldx WITH B!table3.fieldy
IF NOT TABLEUPDATE(F.,.T.,"A!table1")...

but I would use aliases instead.
USE A!table1 IN 0 ALIAS Atable1 ....
and then use Atable1 instead of A!table1.

The integrity checks will remain within each DBC, however.
You can create a free table that can act as a bridge between two fields in tables in the DBCs and write your own tracking code.