The short answer is that is: that is not possible. An aggregate measure contains some form of aggregation within it and thus would depend on the dimensions in the view to figure out how to appropriately summarize rows of information. Can you tell me what you are trying to achieve with these two data sources? That might be a better starting point for this issue.
I am confident that what you want to accomplish can be done in Tableau, but in order to provide assistance, you will need to provide additional details on your situation. A packaged workbook, a .twbx file, that represents your situation and details on the logic you would like to apply, and the results that you want from your sample data would enable assistance.