looping record by record and processing

I have 2 tables they are identical what i need to do is when i make a update on one table the other table needs to reflect that same table. so lets say i insert into table A i need to look in table B if the record exist if it doesnt insert it if it does update it and if it exist in table B and doesnt exist in table A delete the record but i have to do this record by record..can anyone help me with thisUse a trigger...

You'll probably have to do an initial clean up first...|||Please brett can you show me how to do this in code...i have figured out i will need a triger but i have been trying all kinds of stuff and not getting anywhere code wise...