Learning a Field's Properties Using SQL

I'm using SQL within Visual Basic in conjunction with Access
databases. Say I am about to insert a record with a long string for a
particlar field. It would be useful to prevent errors to first
interrogate the DB to learn the maximum permissible length of that
field, and only then proceed to write the record. I believe I've seen
that done   -- i.e., get Access field properties -- but don't know the
SQL syntax. Can anyone give me a sample?

Thank you in advance.
Steve