>What is the most efficient way of handling this?
>Assuming I have a compound PKEY or CANDIDATE
>should I do a SEEK before modifying a one of
>the components or is it more efficient to trap
>for the error?
>
>   ...kt

I usually do both. Not sure, it's the right approach (I had several discussions here about this problem), but this is how it works in our system (single tier):
I have a special textbox class, which checks for uniqueness of the entered value (if it's not unique, User can correct it immediatelly) and our form also has some mechanism to deal with errors on the save stage.

Let me know, if you want more details.