Marketing Cloud: pass system VAWP view_email_url as a parameter to VF page

We link to a customer profile center like this:

SET @clientkey = [Id]SET @clientkeyencoded = URLencode(@clientkey,1,1)SET @URLprofile = Concat("https://vf_page_name.secure.force.com/profile?source=marketing_mailing&id=",@clientkeyencoded)

and then insert the link:

href="%%=redirectto(@URLprofile)=%%"

Under certain circumstances, the VF page should forward to the web version of a newsletter after saving / updating data. To be able to do so, I wanted to pass the system-generated VAWP link in the background, so the VF page knows where to forward when the source equals "marketing_mailing". I tried to amend the standard view_email_url like this:

source=marketing_mailing&id=",@clientkeyencoded,view_email_url)

but this doesn't work.

Do I have to amend it in the redirectto somehow?

Any idea is highly appreciated.