Hi Swapan,
If i understand your question correctly you want to debug the code, written after you press enter or cancel in pop up window.
Please follow the below steps:
1) Add the below full text in a notepad and save it in desktop.
[FUNCTION]
Command=/H
Title=Debugger
Type=SystemCommand
2) Now when the pop up window comes just drag and drop this notepad file in the pop window.
Now when you do any action from pop up window like enter/cancel then debugging screen will be triggered.
Hope it helps.