I'm still researching, but is there a way to set up a minimum quantity ordered to receive the "special discount"

For instance, I have mugs that have a min order quantity of 48 for 2.00ea. I put that mug on sale until from Oct. - Jan. 1st. for 20% off but to get the discount, you have to have a min quantity of 90. How can I set it up to show the min quantity as 90 only during the sale, then it will revert back to the original min quantity of 48 after the sale ends. I do not want to go back and update the 300 products by hand after the sale expires.

thanks in advance.