Hi Kate,
Certainly it's possible but need custom programming. You can contact us via Support page (http://www.viart.com/support) and discuss this feature in more details.
Ideally, we'd also like the quantity to be a text field instead (so the user could choose 682, or 2851, not just predefined numbers). Is there any support for these features, or can you recommend a programmer to help integrate them?
This option is available here Administration > Products > Products Settings. See Products Quantity Control and Basket Quantity Control settings.
WBR,
ViArt Support Team