UPDATE Trigger on multiple tables

Is it possible to have a single trigger on multiple tables
simultaneously? Example:

CREATE TRIGGER emp_cust_stamp BEFORE INSERT OR UPDATE ON employees, customers
FOR EACH ROW EXECUTE PROCEDURE last_updated_stamp();

I tried something like the above but get an error message at the comma. I tried using the keyword AND as well.
I couldn't find anything on this in the docs. I have many different tables in my databases which all have a
"last_updated" field and it seems less tedious to be able to enforce updating this trigger database-wide using
just one trigger. Is it possible?

Ferindo