I'm Joomla web developer from Europe and I have been doing Joomla websites for the last 10 years. I become an expert in maintaining, editing, creating and updating all Joomla extensions, including templates and modules.
I use Virtuemart on my e-comemrce sites, and I ll be able to change the constants.
I will be able to fully fill your project in best possible way, and I'm ready to start.
Check my rating and past projects - they are 5 star Joomla tasks.
Cheers!