delete cascade question

Hi All,

I am using a cascade delete on the following table:

vid vname parentname
1 n1(at)test(dot)com
2 n2(at)test(dot)com n1(at)test(dot)com
3 n3(at)test(dot)com n1(at)test(dot)com
4 n4(at)test(dot)com n1(at)test(dot)com
5 n5(at)test(dot)com n3(at)test(dot)com

So the delete cascade states if I am deleting a row whose vname matches
the parentname delete those rows and it works fine.

I just changed the values of parentname (but the vname values stay the same)

vid vname parentname
1 n1(at)test(dot)com
2 n2(at)test(dot)com n1
3 n3(at)test(dot)com n1
4 n4(at)test(dot)com n1
5 n5(at)test(dot)com n3

Is there a way to do the same cascade delete with these values? I can
select the correct info from vname in a query:

select substring(vname, from 0 for position('@' in vname)) from table1;

This works, so I tried to put that in the cascade but it failed.

Is there any way to accomplish this?

Thanks

Glenn MacGregor