I've been trying to add a constraint to an Access table which restricts 

the user from entering a number in a field more than once within the same 

year. The tables consists of the following fields:





costing

-------



cnumber      - Number(data type)

costingdate  -  Date/Time



The statements below are not working:



1. alter table costing add constraint numberyear           unique

(cnumber,datepart('yyyy',costingdate));

2.alter table costing add constraint numberyear  

  unique(cnumber,year(costingdate));



Is there any way to enforce such a constraint?



~Ryback