Setting up product variant to default to a specific quantity

Hello, 

I have a product that needs to have its unit price adjust based on quantity. Is there a way to accomplish this?

Currently I have the product just setup with 3 variants. A variant for 1-11 units, one for 12-199 and one for 200 or more. I have a rate for each but this concerns me as the customer still has the option to select the bulk rate of 200 units but still enter a lower number of units in the QTY field and purchase a lower number of units at the bulk rate. 

Any help would be appreciated. Thank you!