It's possible but I've never done exactly the same thing. You would create a combobox control instead of using data validation. You would associate the control with the same range on a worksheet that you used to create the data validation (you could also write VBA code to populate it). You configure the combobox MatchEntry property to have the behavior you want (default is to match against every character typed, that will give you your autocomplete). Then when the user completes the selection, you have to capture that result and put it where you need it. You have to figure out how to handle things like the user types in a character that doesn't match anything in the list.
That's just a broad strategy. If you really want to pursue this provide some more details (sample workbook is always good) and I (or someone else here) might have time to write some code up for you.
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