Software Customization

I'm looking for an experienced freelance software developer to help me customize a software solution for my business. The type of software I need customized is customized software, which requires functionality and design changes, but not a complete overhaul. This should be completed in less than 1 week. The perfect candidate for this job should have knowledge of software development tools and techniques. They should also possess the ability to debug problems effectively and determine the best solutions to improve upon the existing program.