Bookmarking in the middle of the course

I have a course which is 100 slides and i want learner not to repeat slides in case there is an issue with network. The option "send data on each slides" doesn't works in a way we want.

So just to elaborate - If the learner is on slide 20 and network goes off, we want him to start from slide 20 when the network is resumed and he relaunches the course.

I have tried couple of java script codes on the slide enter. but they haven't worked. I found them on the following article -

Resuming after a Communication Error with LMS

In case some one has solution to this, request you to please advice.!

Thanks.

Himanshu