>set a temporary error routine, attempt the INSERT, and trap for error 1884.
>
>This might be great for the new TRY/CATCH in VFP8.

I have done a simple cursor with an index on candidate. Here's the code:

TRY
   MESSAGEBOX('Attempt')
   INSERT INTO Temp (Numero,NoProvince) VALUES (1,1)
   MESSAGEBOX('Executed')
CATCH
   MESSAGEBOX('Failed')
ENDTRY

On the first run, it inserted the record. On the other run, it failed. All is working ok. I'll try that in the application.