Showing popup on delivery option and using external API

[sagar_kacha]

I want to add custom functionality in Checkout. Is there any way to open popup while clicking on the Pickup delivery option? Also, I want to use an external API in the popup. Can I use Shopify Functions to achieve this? If yes, then how.

If there is any other way, suggestions are welcomed.

Thank you. Appreciate it.

[sabeeh]

Hey 
You can use checkout extensions. 

[sagar_kacha]

can you please tell me how?