Dynamic Data Refresh - Power BI Service

I have a similar stored procedure where i need to pass along a parameter for start and end dates that i'm calculating in a function. 

So my source line looks like:

Source = Sql.Database("MyInstance.database.windows.net", "SQL-DW-PROD", [Query="Exec MyDataBase.[sp_MyProcedure] 0, " & fnStartDate & ", " & fnEndDate", HierarchicalNavigation=true, CommandTimeout=#duration(0, 0, 90, 0)])

Then i have another 2 queries as the functions, named fnStartDate and fnEndDate where i can calculate those exact dates.  They can look as based as this:

let
    Result = "'2016-01-01'"
in
    Result

Or you can get more complex and calculate a date like this:

let
    CurrentMonth = Date.Month(DateTime.LocalNow()),
    CurrentYear = Date.Year(DateTime.LocalNow()),    
    Result = Number.ToText(CurrentYear) & "-" & Number.ToText(CurrentMonth) & "-03"
in
    Result