I need help to add a timestamp to B2 in TIMESTAMP sheet if I imported CSV file in IMPORT FMS Sheet, I want to know when the last time my colleagues update the sheet
I’m not an expert using AppsScript but I gathered info from internet, and I managed to add basic timestamp to it

function onEdit(e){

  var row = e.range.getRow();
  var col = e.range.getColumn();

  if(col == 1 && row > 1 && e.source.getActiveSheet().getName() == "TIMESTAMP"){

    var currentDate = new Date();
    e.source.getActiveSheet().getRange(2,2).setValue(currentDate);
  }
}

But the problem, it won’t work based on Imported file, instead it works only if I edited cell A2 in TIMESTAMP sheet manually (typing or copy paste from certain cell in IMPORT FMS sheet)
Here is the Sample Sheet and here is the Test File that I want to import

Is there additonal script to make it work if cell B2 in TIMESTAMP sheet change based on cell reference in IMPORT FMS sheet when I import file in IMPORT FMS sheet?
Thank you for your help