How to limit the approval of requests on the Web-portal

So what we have:
There is a multi-requested resource for IT-Shop
There is a certain workflow for this resource.

I expect that at the execution step, when you click on the reject button, a popup will appear.

My logic is this: in the PWOHelperPWO table there is a link to QERWorkingStep, in which I can find out Ident_PWODecisionStep, whether it contains “Execution” and displays a message. But I don’t know how to do it exactly. Has anyone encountered a similar problem?