I have figured it out myself. thanks
I want to run a competition in which i want that the total sales should not be effected and the number of fake leads should also be reduced. So at the end of the month i want that total conversions should remain same or maybe reduced to only 5% of sales in last 3 months' trend. but the fake leads should go down immediately.
The winner will be the person who reduces the fake leads and still manages to get same rate for successful conversions.