I been converting an old IIS site to use DNN, How do i get the querystring parameters to be passed thru to an external page

The following link as been issued and needs to be maintained  

 http://xyz.com/support/update?Product=A  

on the old IIS site the folder support/update had an index.aspx file which displayed different content based on the Product parameter, due to the complexity of this page it isnt going to be converted to DNN in the short term.

I've tried creating a DNN page support/update with a link to the external page  i.e http://xyz.com/support/update/index.aspx but the querystring parameters are lost.

How do i get the querystring parameters to be passed ? or is there any alternative method to get to the old page

An external user may use the URL http://xyz.com/support/update?Product=A  , another may use http://xyz.com/support/update?Product=B

when this was done using an IIS website, the default document in the folder /support/update i.e index.aspx would be loaded and that would process the query string and adapt the page based on the Product.

Under a DNN site, it wants to load the page support/update, i've specified the External URL on that page to be http://xyz.com/support/update/index.asp , somehow i need to get the original query string to be appended to the External URL, it can't be a fixed querystring

I got around it by creating a URL rewrite rule to insert '/index.asp' after 'update', so that the url was update/index.asp