Advertising banner impression/click tracking

I need someone to design a software for tracking advertising banner impressions and clicks. We are an advertising firm that represents and places advertising banners on behalf of our client and need to track the effectiveness vs cost of the adverts. This development will give our clients a tool to track the impression and clicks, and CPM (cost per impression) / CPC (cost per click) of the banners. Please demonstrate and explain your understanding of the brief with your bid. Thanks.