You might start with Calculating Business Hours Between Two Timestamps
If you run into any issues, we may be able to help you more if you can share a workbook demonstrating the issue. Instructions for creating a packaged workbook can be found at the following link: http://kb.tableau.com/articles/knowledgebase/sending-packaged-workbook
A quick method to anonymize a workbook is to hide any fields containing sensitive information before the data source is extracted. Hidden fields are not included in the final extract.
Hope this helps!