I able trying to build a bar chart that has several "accounts" performances over say two quarters. So far I have accomplished this. However, located in another table in the dashboard is the baseline data from the pervious year. What I want to accomplish is plot this baseline data as bar in the bar chart that I made or plot this baseline data as a trend line over its' corresponding account. I believe the solution lies along the lines of forming a relationship between the 2 data sources and then having some kind of calculated field. I'm not sure though.
What you're asking sounds reasonable but it's tough to answer without a workbook or at least screenshots. If you provide a packaged workbook with sample data we can take a look. If you have sensitive data, I would check out Anonymize your Tableau Package Data for Sharing.