Change the height of one item-item of collection-repeat

Hi everyone !

I am using collection-repeat in order to create a calendar. I won’t go into details, but here is what looks like a month :

Simple, right ?

What I want is when one clicks on a day, for instance 16, there is a separation between two weeks and more infos about the day display.

Each week in an item of my collection-repeat. I saw the problem in changing the height dynamically of item in collection repeat. But what I want is not the height to adapt to multiple height, just when I click, change the height of one of the item.
It’s better if I can change the height in %, but in px is not a big problem. (Even if I don’t see in what it could change anything).

If anybody have any idea, that would be very helpful. After reading many posts in this forum, nothing helped and I kinda run out of steam.