Message on process success or error

Hello,

I have an Interface. Within this interface user uploads excel file containing some emails. Next user submits excel and process model is started. 

Interface is published on a website. 

When user uploads excel and clicks submit interface looks exactly the same, no message if the process was successful or anything.

I would like to create new popup window or some message when user submits and run process with uploaded excel. 

I tried using onSuccess but it didn't work. Do you have any tips? 

My code looks like this: 

a!localVariables(
  local!cancel,
  local!WczytanePlik,
  local!NazwaPliku,
  local!Pracownicy: if(
    a!isNullOrEmpty(local!WczytanePlik),
    {},
    rule!EA_TEST(local!WczytanePlik)
  ),
  a!formLayout(
    label: "Wczytaj plik",
    contents: {
      a!sectionLayout(
        contents: {
          a!textField(
            label: "Nazwa pliku",
            labelPosition: "ABOVE",
            instructions: "Wprowadź nazwę pliku",
            value: local!NazwaPliku,
            saveInto: { local!NazwaPliku },
            refreshAfter: "KEYPRESS",
            required: true,
            validations: {},
            inputPurpose: "NAME"
          ),
          a!fileUploadField(
            label: "Plik",
            labelPosition: "ABOVE",
            instructions: "Wybierz plik z komputera",
            target: cons!EA_WCZYTANE_PLIKI_POINTER,
            fileNames: local!NazwaPliku,
            value: local!WczytanePlik,
            saveInto: {
              a!submitUploadedFiles(),
              local!WczytanePlik
            },
            required: true,
            validations: {}
          )
        }
      )
    },
    buttons: a!buttonLayout(
      primaryButtons: {
        a!buttonWidget(
          label: "Zapisz",
          submit: true,
          style: "PRIMARY",
          saveInto: {
            a!startProcess(
              processModel: cons!EA_send_email_wrapped,
              processParameters: { pracownicy: local!Pracownicy }
            )
          }
        )
      },
      secondaryButtons: {
        a!buttonWidget(
          label: "Anuluj",
          value: true,
          saveInto: local!cancel,
          submit: true,
          style: "NORMAL",
          validate: false
        )
      }
    )
  )
)