My question maybe is simple, but anfortunatly I don’t know how to answer it.
How can I create a variable in a hook function and then pass a PHP variable from within the function to my Template in order to use it in the form of {VARIABLE_COMES_FROM_HOOK}
Search in hook categories http://docs.whmcs.com/Hooks
There are hooks that return variables to tpl and other that don’t do that