referencing other INSERT VALUES columns inside the insert

I know that this is something that can't be done...

CREATE TABLE test (c1 int default 0, c2 int default 0, c3 int default 0);
INSERT INTO test (c1, c2, c3) VALUES (3, 7, c1 * c2);

Is there a known trick to work around it (so that the values inserted into
c1 and c2 is referenced back to c3), other than (obviously!) copying the
literal values into the VALUES string?

To be clear, the SQL is generated dynamically based on data, so I can't
just create a view for the calculated column (it won't always be
calculated!).

Thanks!

Geoff