If page template is

Hello, this is my first post nice to be here.

My question is related to implementing Conversion codes for Google, Facebook,etc. I know the I can place it in orderform templates where it says

{if $ispaid}
<!-- Enter any HTML code which needs to be displayed once a user has completed the checkout of their order here - for example conversion tracking and affiliate tracking scripts -->
{/if}

However as far as I know and faced that for each update of WHMCS the code is removed so I have to re-add it manually. I've checked the forum if anybody has asked such question before and even Google but no luck.

I'm trying to add the code into footer.tpl file however with certain conditions the apply.

My target is to implement it when page template is complete.tpl and marked $ispaid.

Something like this

{if $pagetemplate == 'complete.tpl' && $ispaid }
<!-- Enter any HTML code which needs to be displayed once a user has completed the checkout of their order here - for example conversion tracking and affiliate tracking scripts -->
{/if}

Is that possible and how? Thank you in advanced!

if you can do it using a hook, you shouldn't need to continually edit the templates after an update...

https://forum.whmcs.com/showthread.php?93446-Add-Facebook-Tracking-to-Checkout-Page