Dyanamic Sql

Hi I was building a dynamic sql with output please tell me where I am wrong.
Or Tell me right way to do it

My table name is variable (Stock name)
I want close price for given Stock

CREATE PROCEDURE SP_GET_CLOSE
@TableName as varchar(50),
@close_price as varchar(50) output

AS
Declare @SQL NVarChar(1000)
Declare @high varchar(50)
SET @SQL = 'Select top 1 @close_price = [close] from '+ @TableName+ ' order by trade_date desc'

print @SQL
Exec sp_executesql @SQL, N'@close_price varchar(50) output' , @close_price
GO