How to compare to a list exactly

Hello, 

I currently have a drop-down list that is populated with names and numbers from a report. If the number is typed into the drop-down, it'll search and find it. 

Is there a way to compare to the list (report) exactly? I'm not attached to having a drop-down list if a text or numeric field will work and right now it'll find the closest match but is there a way to have an error pop up if the match is not exact?

Thanks.