In Part 2 we showed how you eliminate any double data entry by making your online store visible to your FileMaker solution by using the ESS (External SQL Data Sources) feature of FileMaker Pro/Server, allowing users to see online orders on a normal FileMaker layout.
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Look for the 2 other parts http://www.scoop.it/t/learning-filemaker?q=FileMaker+and+eCommerce+Integration