Catching A/R Invoice confirmation MessageBox user selection

Hi, I`m trying to run an add-on when the A/R invoice is added, but I need to catch what the user select in the confirmation message MessageBox.

the following code is for read the data from the form, but I need to catch the selection to this MessageBox to execute the add on or not.

if (pVal.FormType == 133 && pVal.EventType == SAPbouiCOM.BoEventTypes.et_ITEM_PRESSED && pVal.FormMode == 3 && pVal.ItemUID == "1" && pVal.Before_Action == true)

{

// read data form AR Invoice form

}

How can I do that?

Best regards