Modify a html (used in proxy) to intercept url being loaded to compare if it's in whitelist

Refer to attached html file which I learnt from my secure browsing vendor will be used in the proxy server
(this proxy is being pointed to by our IE & Chrome browsers).

We are supposed to do whitelisting/blacklistg in the proxy but it's currently not working (got various invalid
certs & website insecure errors when going thru proxy) though this html somehow seems to be activated/run.

My plan is just to set the proxy to not have any whitelist/blacklist but instead this html will check against a
txt file for a list of whitelisted sites/URLs   &  if the URL/IP address that is going to be loaded is in
c:\folder\readonlyfile_whitelist.txt, allow the user to continue to use IE to load it, otherwise, launch/load it
using the secure browser  (refer to the line in the browser ie  garrison://url_to_be_loaded  ie :
   <a href="garrison:%U[URL/URI]">%U[URL/URI]</a>


I'm probably referring to a similar solution in links below:
  https://stackoverflow.com/questions/1686687/how-can-i-get-the-destination-url-for-the-onbeforeunload-event
  https://stackoverflow.com/questions/5190021/track-the-new-url-being-entered-in-the-browser


The URLs in the c:\folder\readonlyfile_whitelist.txt   may contains wildcards so need the
coding needs to handle this.

Eg: readonlyfile_whitelist.txt  contains the following:

*.trusted.com*
*192.168.*

then when the user is loading the following URLs, it will be treated as a whitelisted url
& allow him to continue in IE:
  https://www.trusted.com/sub1/page.html
  http://192.168.33.55/login.aspx

otherwise, the command garrison://URL   will be used,  launching the secure browser
& load the URL in the secure browser
scbrw.html