Username in Connection string

Hello, 

Fairly new to Power BI and I was wondering if there is a way to add the connecting username to the connection string.

Source = Sql.Database("DB", "Table", [Query="#(lf)EXECUTE [dbo].[PowerBI_Test] username = 'Login Username here'#(lf)"])

I want to pass the username to a stored procedure. 

Thank in advance for any help