Interupting a process screen process with a web dialog.

You can ask for confirmation before the process starts using SetParametersDelegate:

using PX.Data;
using System.Collections.Generic;

namespace Sprinterra.Examples
{
    public class URProcess : PXGraph<URRecord>
    {
        [PXVirtualDAC]
        public PXFilter<URFilter> Filter;

        [PXFilterable]
        public PXFilteredProcessing<URRecord, URFilter> ProcessingView;

        public URProcess()
        {
            ProcessingView.SetSelected<URRecord.selected>();
            ProcessingView.SetParametersDelegate(AllowProcessing);
            ProcessingView.SetProcessDelegate(list => Process(list));
        }

        public bool AllowProcessing(List<Record> records)
        {
            //You can filter when this check is invoked
            if (Filter.Current.ActionID != Actions.ApplyPrepayment)
                return true;

            return ProcessingView.Ask(Constants.Title, Constants.Body, MessageButtons.YesNo).IsPositive();
        }

        public static void Process(List<URRecord> records)
        {
            // your processing logic
        }
    }
}