You can use DISTINCT. It could be sloww if table is big.

SELECT DISTINCT CourseCode FROM StudentReservations 

>I have a table with contains students reservations and this table has a field with contains the course
>code (there are several courses and more courses can be added )
>
> I would like to grab all course codes in a combo, and then use the combo
>to filter the records that show on the grid as a select a state on the combo
>
>Moises