Set Minimum Price

Wondering if someone can help with this:

I am setting up a payment form for bulk purchases and would like to set a minimum price without restricting the quantity a user can select. Otherwise stated, if a user selects a quantity that would come to a total amount under the minimum price, their total would automatically bump up to the minimum price point automatically.

For example, the price is $20 per item with a $100 minimum purchase. I want a user to be able to only buy 2, but their total price would come out to $100.

I hope this makes sense!

Update: Figured it out!

Thanks Douglas. Would you be able to share your solution here?