Difficult problem with fine grain user access to table. Any ideas?

We have a table emergency_responders, with columns

empnum
emer_role
date
office

the office column can have 7 different values (Dallas, Chicago, .., Detroit) or null.

We want to give access as follows:
Create 7 accounts - 1 for Dallas, 1 for Chicago, 1 for ...: each has full read access but write access only if the office column value is blank or is the same as the city the acccount is for.

So for example a row with an office of Dallas, can be read by all accounts but only updated or deleted by the account set up for Dallas.

A row with an office of null, can be read by all and updated or deleted by anybody

Any idea of how this can be done. Note that access might also be thru a view to this table unless its impossible.

we are using Oracle 8i version 8.1.6 Received on Mon Mar 11 2002 - 15:02:10 CST