If you want to connect to an Access Database to Postgres you can install the ogr_fdw extension. This awesome Postgis add-on utilizes the Foreign Data Wrapper functionality of Postgres to connect to external spatial data sources -like Access and many others.
Provided you have the OGR MDB Driver installed, ogr_fdw will allow you to connect to your Access Database by defining a foreign server:
CREATE SERVER access_server
FOREIGN DATA WRAPPER ogr_fdw
format 'MDB' );
You can define all of the foreign tables in the Access Database in one command via:
CREATE SCHEMA mymdb;
IMPORT FOREIGN SCHEMA ogr_all
FROM SERVER access_server
Now you can query your Access Database tables as you would any normal Postgres table:
SELECT * FROM mymdb.mytable
Since the Foreign Data Wrapper merely connects to the Access Database -and doesn't actually import the data into Postgres directly -any saved changes you make directly to a table within Access should be IMMEDIATELY visible in Postgres -which hopefully fits your definition of "dynamic". However, if you modify the table definitions within the Access Database, you will obviously need to make corresponding changes to the foreign table definitions in Postgres.