set up pop-up on Custom Action set in Service Portal Setting

Hi,

I have configured custom action under Service Portal Settings->Configuration Settings->Custom Actions to abandon the Request. This action will be visible on Service Portal page for the requests which user has created.

Now User want on clicking action button, pop-up message should appear confirming user wants to continue abandoning Request, as user had abandoned few requests by mistakenly.

I dont see there is a way to configure validation under Service Portal Settings->Configuration Settings->Custom Actions.

Please help if there is any workaround.

Thanks,

Darshana