Need to have a pop-up message based on which continuing the groovy rule or not in a data form

Summary:

Hi,

We are facing the following challenge:

There is a data form where users can change a certain amount.

Once they save, a groovy rule runs to address an associated target value in a specific block.

Most times the associated target value will not change from the current amount, yet there are some cases where it should change.

When this happens, we would need to advise the user of the potentially changing amount, asking them whether they are sure about their input. 

If they say so, the rule will proceed and change the target value, if they say no, the rule will not proceed and the input amount will not be saved.