How to trigger on the attach button when we click it

Frappe Framework
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1

Hello,
I want to trigger custom code when the attach button got clicked.

How to trigger it when we click on the attach button?

image

3

This will trigger when the file URL is saved. I want the trigger to occur when the popup appears so that our custom code executes at that time.

4

Check the form script and set it according to the scenario.