How to Lose a Guys in 10 Days (2003)

Andie (Kate Hudson) who longs to write about political issues but finds herself writing for women's magazine called Composure. She is challenged by her friend Michelle (Kathryn Hahn) after hearing her latest dating laments to write an article "How to lose a Guy in 10 Days" and she herself have to experienced dating a guy and losing him.
However, Benjamin Barry is an advertising executive competing with his two female co-workers for a major diamond campaign merchant. He cuts the deal to find a girl who falls in love with within 10 days.
They found themselves falling in love with each other and failed with their different missions.