Center button in a button block

Hi all,

In a course, I need to send learners to a webpage when they finish the course.

As there is no way of adding a link to the "continue" button, I was planning of using the button block to make that interaction.

What I would like is to have the button centered (I don't use any text) in the page. For now it's on the right.

Any idea if there's a solution to do that ? (Don't want to do css modification if someone already has a solution ;) )

Thanks