Highlight Time in a Timeline

I've made a simple sheet to track my daily activities.
As you can see from the document attached, my timeline go from 9 AM to 2 AM. Ideally I'l like to draw a border every 30 minutes as the time changes.
See the sheet in order to understand better.
Obv I have no clue how to do it, even if I used the forum search feature.

Ty in advance