Dynamic variables: PageInject Plugin or page.find

Hi
Is there any way to use variables with [plugin:content-inject] or page.find(url)?

I.e.
{% include 'timetable.html.twig' with {'neededPage': page.find('/timetable/first')} %} - works just fine

but
{% set gymUrl = "/timetable/first" %}
{% include 'timetable.html.twig' with {'neededPage': page.find('#{gymUrl}')} %} - nope
{% include 'timetable.html.twig' with {'neededPage': page.find('{{ gymUrl }}' )} %} - nah

or (with twig processing(first) enabled,)
plugin:content-inject - works

but
{% set gymUrl = "/timetable/first" %}
[plugin:content-inject]({{ gymUrl }}) - no

Just a quick guess, but do you have to leave out the "{{ }}" around gymUrl?

{'neededPage': page.find( gymUrl )}