Using a Mix and Match dicount and applying as a sale

I have group of items tha tI need to put on sale. I made a discount Mix and Match 3/99.99. I need to run this sale fro about 2 weeks not a perminat price structure. The work sheets do not allow me to use a discount as a sale. There are about 75 items and I don not want to go thrue each one and apply the discount and then remove it later. Mike Callaway