Inserts using plpgsql

It seems I can insert only a single field using plpgsql.

INSERT INTO journal (j_date, evntnmbr) VALUES (jdate, param); Fails

INSERT INTO journal (j_date) VALUES (jdate); Works

j_date is a date field while evntnmbr with it's associated variable, param,
are integers. Can someone explain this for me please?

Thanks.