how to create a sequence in a stored proc?

I need to create a sequence in a stored procedure.

First I need to select a value from a table and set the sequence start
value to that value.

We have a table that does not have a sequence on it, so I want to select
the max value, increment by one
and then start the sequence there.

We have to do this on three databases, I have figured out how to do this
in Oracle (build a string and the EXECUTE IMMEDIATE <myString>, but have
not figured out how to do this with PostgreSQL.

any ideas?

thanks


J.V.