Script to autologin portal when offline wih UGS40

The USG40 is in a challet/cottage on a holiday park.

There is a lan connection in the challet, to activate the internet whe have to enter a code on a webportal. (Also for  the WiFi on the holiday park.)  Instead of entering the code we can also use the URL:  https://aplogin.com/?code=ABCDE123&url=https://somewebsite.com&ip=192.168.10.12

On random times whe need te reactivate the connection to gain acces again to the internet. (We also use the internet to remote control the Heating system).

What we would like:

If the WAN1 is offline. (As example no ping response from www.google.com) the UGS has to call the url https://aplogin.com/?code=ABCDE123&url=https://zyxel.com&ip=192.168.10.55  every 5 minutes.

What we think is great?

Modify  the url in the script:  https://aplogin.com/?code=ABCDE123&url=https://zyxel.com&ip=192.168.10.12
But instead of ip 192.168.10.12 we would use the WAN adres as variable .   
https://aplogin.com/?code=ABCDE123&url=https://zyxel.com&ip="Wan1 IP"