Help needed with DAX Switch Statement multiple columns (Picture included)

I think I will abandon doing it using the big SWITCH approach, as the circular dependency error is just getting too difficult. 

Just needed to clarify that each line within SQL server represents an individual saleperson's stats for an indivudal day, ie sale made for the whole day, total amount of calls for the day etc. Right now I am looking at an aggregated monthly view and have a column that is the summation of everdays sale ammount so I can view it at a monthly view. Using the aggregated monthly sales figure, I just need help with finding the corresponding grading provided by HR.

If you or someone can please help with teaching me how to link up a performance grading table, and then using the [Sales Amount] month CALCULATED MEASURE to look up the corresponding grading that would be fantastic. 

😢😢