casting Bangla characters to NUMERIC

Hi

I have an interesting problem.  I have a string field in a table which
(sometimes) is expected to contain numeric values  ie. a cast of the
field to INTEGER is supposed to succeed.

My issue is that the application is running in Bangladesh, and
sometimes the users have entered values using Bangla characters.  eg.
"৮" rather than "8".  (Note that this shouldnt have been possible to
enter in the first place, but we can ignore that for now.  They are
there, I have to somehow deal with it.)

Is there a way with LOCALE settings to get this cast to work
correctly?  Currently I get:
postgres=# select cast('৮' as INTEGER);
ERROR:  invalid input syntax for integer: "৮"
LINE 1: select cast('৮' as INTEGER);

Regards
Bob