Create inversed rounded border button

Hello!
I am trying to create inversed rounded corner button widget with help of materials.
Like this
image

I use instanced material for this.
But to make my button be any width and height and without stretching borders I have to set aspect (widget width / widget height) to my material instance. I found that I can calculate it with node “get cached geometry” → “get absolute size”. But this flow works only if i “Delay” some time after widget creation. Without delay it returns wrong zeros.

Theese are my BPs:



Any help please.