Unique values within a combo box

[Lofi]

Hi,
Im working on a form within a database for school alumni and I'm stuck.

The values that are in my combo box duplicate, and I was wondering how I could get these values to show up only once within my combo box (to not duplicate). Thank you

 

[Axis]

Go to the query that is the source for the combo box and in the form properties window change Unique Values to Yes.