hi, I have been magento developer for over 5 years and have lot of experience on this field, I read your requirement and really interested, I had many projects for theme, layout and extension customization, very familiar with the core of magento, I can create a category attribute for that CMS block, when you set it to yes, that block will be shown on category page. I am sure I can finish your project perfectly, hope that we can create a long term relationship, please view my profile and contact me to discuss more, thanks.
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Best Regards,
Kevin