T-SQL (SS2K8) :: Pass A Column Name Using Parameter In Select Statement

I have a temp table that hosts data from a MDX query, I want to select a column from that table by passing in a parameter and then insert to a new table.

Here's the table structure, let's call it #temp

[Product].[Product Hierarchy].[level 03].[Member_CAPTION], [Measures].[Gross Sales]
Bike, 200
Accessory , 100

I have a table in the DB created as [ProductSales]

Here's what works for me:

insert into [ProductSales](Product, Sales)
Select convert(varchar(20), "[Product].[Product Hierarchy].[level 03].[Member_CAPTION]") as 'Product' , convert(decimal(18,2), [Measures].[Data]) as 'Sales'
From #temp

But in reality the product level is not always on level 03, I want to define a parameter @Product and pass it to the select list.

Here's what I tried to do:

Declare @Product varchar(500) = convert(varchar(20), "[Product].[Product Hierarchy].[level 01].[Member_CAPTION]")
Declare @SQL varchar(MAX)
SET @SQL='insert into [ProductSales](Product, Sales)
Select '+@Product+' as 'Product' , convert(decimal(18,2), [Measures].[Data]) as 'Sales'
From #temp'
Exec @SQL

But it threw me error, what is the right way to do it, is it because the double quote or single quote thing?