How to call _secureURL

I am trying to do redirects to the calling page inside my Coldbox
admin page. If before logging in they will they will not
always be sent to always like they are now. I am using
Coldbox's built in security interceptor. So my question is what is the
syntax to call _secureURL inside of the form using a hidden form
Thanks for your help.

I did a dump of the request collection scope inside the login form and
I see the _secureURL key
when I try and access something besides the index page. I then did a
dump of the session scope and I see it is set to autopurge.
So, it is on being available on the login form page. How can I
override this autopurge setting?

With Luis Majano's help I have been able to solve this.

The first thing I did was to verify that _secureURL was being created
on the secure login form by calling something other than the default
setNextEvent in my handler.
I did this by just pasting the link into the browser window and
dumping the <cfdump var="#rc#"> request collection in the login form.
I could see the link coming back in the _sercureURL key of the request
I then just needed to persist that key to the handler that gets called
when I click the login submit button. The code I used to persist the
_secureURL key is <cfset flash.keep("_securedURL") />

In my login handler I added this code.
Check to make sure _securedURL is not an empty string
      <cfif Len(flash.get("_securedURL",""))>
setNextEvent(event=ReplaceNoCase(flash.get("_securedURL",""), "/
index.cfm/", "")) />
<cfset setNextEvent("admin.index") />
I am replacing the '/index.cfm/' because I am using ISAPPI rewrite to
remove the index.cfm.
Thanks, Luis for pointing me in the right direction