Did you consider using IDENTITY column or uniqueidentifier data type?

>I am working with a SQL server database and I have multiple interfaces that can
>add a record to the database. each interface has its own logic to assign the next unique # to my table. I am having a problem where the 2 interfaces send a new record to my SQL table at the same time I am getting duplicate sequence #'s in the table. I was trying to research how to move the numbering logic into SQL server as either a function, stored procedure or a trigger. Does anyone have any advice on which way I should look at ?