I want to create a default value for a column when new records are added but the default value depends on value of another column and I don't know how this can be best done.

For example, if I have a very simple table with just two character columns of FIELD1 & FIELD2, I want the default value of FIELD2 to be:

1) If value of FIELD1='MOMMY' then default for FIELD2='WOMEN'
2) If vlaue of FIELD2='DADDY' then default for FIELD2='MEN'

How can I go about doing this using either DEFAULT or TRIGGER? TIA.