Tableau allows users to interact with the viz through Parameters and Filters. If the number of sales reps territories is few, it may be possible to use parameters. But they would consume a lot of your viz real estate.
It sounds like you want to be able to change row level data on a published viz. Tableau is primarily a data visualization tool. Doing this sort of data changing on the fly is possible, but it may not be the best tool for the job.
Is there any way you could upload a view of your data/workbook so we can see how it is structured? What is the number of regions/states we are talking about here?