Dynamic sql with output parameter syntax clarity needed - sql-server-2008-r2

Question

I've read several examples of how to return an output parameter with dynamic sql, but all were slightly different in that they created the variable within the procedure, instead of passing them in (I'm assuming this is the root of my problem). I get the error:
Must declare the table variable "#tbl".
When I try to run the procedure below (listed after the test code that executes it). Am I close?
DECLARE #tbl nvarchar(40)
DECLARE #bnch INT
SET #tbl = 'tblDailyPricingAndVol'
EXEC sprocReturnDataPointBenchmark #tbl, #bnch
sproc:
ALTER PROCEDURE [dbo].[sprocReturnDataPointBenchmark] #tblName NVARCHAR(50),
#benchmark BIGINT OUTPUT
AS
BEGIN
DECLARE #sql nvarchar(1000),
#parameters NVARCHAR(100) = N'#tbl NVARCHAR(50), #benchOUT BIGINT OUTPUT';
SET #sql = N'SELECT #benchOUT = Count(ID) FROM #tbl WHERE DateAdded = ' +
'(SELECT MAX(DateAdded) FROM tblDailyATR AS T2)';
EXEC sp_executesql #sql, #parameters, #tbl = #tblName, #benchOUT = #benchmark OUTPUT
SELECT #benchmark
END

Answer 1

There were a couple syntactical errors in my first pass listed above, but the conceptual issue that I needed to resolve was trying to pass the table name (input parameter) in the parameters variable within the dynamic sql. Good example here: Generate dynamic SQL statements in SQL Server
So, my revised, working code is:
ALTER PROCEDURE [dbo].[sprocReturnDataPointBenchmark] #tblName NVARCHAR(50),
#benchmark BIGINT OUTPUT
AS
BEGIN
DECLARE #sqlStatement nvarchar(500)
DECLARE #parameters NVARCHAR(100)
DECLARE #fullStatement NVARCHAR(500)
SET #parameters = '#benchmark BIGINT OUTPUT'
SET #sqlStatement = N'SELECT #benchmark = Count(ID) FROM ' + #tblName + ' WHERE DateAdded = ' +
'(SELECT MAX(T2.DateAdded) FROM ' + #tblName + ' AS T2)';
EXEC sp_executesql #sqlStatement, #parameters, #benchmark = #benchmark OUTPUT
SELECT #benchmark
END