How to convince a manager to take you back?

I worked at a company over 7 years ago but were let go due to low survery scores. I am attempting to work there again due to the economy and the desperate need of funds to support my family. I've applied and taken tests, but no one has called me back to update on an interview. I emailed the highest manager in charge of the facility today in hopes they will reconsider me. I poured my every being in the letter and I hope she calls me back. What are my odds?