Put a cap at some value

This is a dynamic worksheet that i created in which we can enter any number in the box and the value in the week changes based on the number entered. The number entered is generated by making a new parameter which has 1 to 10000 values. The data in the week changes on the basis of the region which i have put a filter for. The goal_qtd column changes for every region and is fixed for every region. I want help creating something in which the value entered in the box is always greater than the goal_qtd. The box will not take any value less than the goal_qtd. Would really like some help for the same.