Mark a few slides as completed based on a pre-assessment result

I am working on a course where the client requires a pre-assessment (before the actual course content). If the learner achieves a 75% or more score, they should be given the choice to skip the current module and take any other module in the course. We are using the player default menu. So, I don't understand how the storyline will mark the "skipped" pages/modules as completed. I didn't find anything relevant on the discussion forums yet. 

One of the discussion threads suggested using a custom menu. But this is not feasible considering the content - there are 12 modules, each with a minimum of 4-5 lessons. 

any help/suggestions are welcome.