Making a point coincident with the last instance of a sketch pattern

sam_one

How do I make a point coincident with the last object of the sketch pattern, so that it moves when the amount of the pattern is changed?

toothbrush holder | Part Studio 1 (onshape.com)
so I have this part, where I use a variable (called Brush_count) and a sketch pattern to describe the slots in the rack.
That bit works fine. Now, I want to add the actual body of the rack around the slots.
The body should go around the slots. So, when I change the amount of slots, the rack should resize accordingly.

I tried to make the top-right point of the body rect coincident with the last slot.
This works, but when there are less or more slots, it doesn't update its position, and the coincident turns red.

any help is appreciated, even if you don't know for sure.
(even a tiny nudge in the right direction makes a difference!)

NeilCooke

Since you already have a variable, drive the position of the "point" based on #Brush_count * #WhateverTheDistanceIsBetweenEachSlot

NeilCooke

Since you already have a variable, drive the position of the "point" based on #Brush_count * #WhateverTheDistanceIsBetweenEachSlot