row-level locking

Hi,

we need to prevent write access for a single row of a table for a short time.

We found a short description for the "SELECT FOR UPDATE" statement:
"perform exclusive locking of selected rows"

Now my question: Is this a good method for our purpose?

Assuming that we lock our row with
"SELECT FOR UPDATE FROM <table> WHERE <our condition>",
how can we unlock it later?

Do we have to put the whole thing in a transaction (which may be tricky from
within a VB-Application...)?

Thanks a lot,
Markus