How do I make this function in Google sheet run "every minute"?

Question

What I have:
1_I have timezone in IANA format like Asia/Kolkata, Asia/Amman and so on.

2_I also have the below code pasted in script editor to solve my first problem. It is prepared by user ASyntuBU. I am really thankful to this user. Now, I have a new requirement.

function getTime(timeZone) {
  return Utilities.formatDate(new Date(), timeZone, 'MM/dd/YYYY hh:mm a');
}

What I want:
1_I wish to get the local time of each timezone refreshed every minute just as now() does, that is no reload of the web-page.

2_Also, I want the output in the cell in Date and Time format so that I can subtract two "time" output.
PS I am not from coding background but I will do my best to do as instructed. Please help

Edit 2:
Point 2 solution - This has helped me to get output in date format. If this is correct, how do I get it solution for point 1

function getTime(timeZone) {
  var a = Utilities.formatDate(new Date(), timeZone, 'MM/dd/YYYY hh:mm a');
var b  = new Date(a)
return b
}

Edit 3:
It does not refresh every minute. What is the syntax error? Please help

function getTime(timeZone) {
  var a = Utilities.formatDate(new Date(), timeZone, 'MM/dd/YYYY hh:mm a');
var b  = new Date(a)
 return b
ScriptApp.newTrigger("getTime")
  .timeBased()
  .everyMinutes(1)
  .create();
}

Edit 4: To change trigger from every minute to onEdit. Is this code correct?

function clock(){
  var chk = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Course').getRange('A1');
  chk.setValue(!chk.getValue());
}

function getTime(timeZone) {
  var a =  new Date(Utilities.formatDate(new Date(), timeZone, 'MM/dd/YYYY hh:mm a'));
  return a;
}

function createEditTrigger() {
 ScriptApp.newTrigger("clock")
   .forSpreadsheet(SpreadsheetApp.getActive())
   .onEdit()
   .create();
}

Answer 1

Try for instance

function clock(){
  var chk = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Sheet1').getRange('A1')
  chk.setValue(!chk.getValue())
}
function getTime(timeZone) {
  var a = Utilities.formatDate(new Date(), timeZone, 'MM/dd/YYYY hh:mm a');
  return a
}
function setTrigger() {
  ScriptApp.newTrigger("clock")
  .timeBased()
  .everyMinutes(1)
  .create();
}

and put a dummy parameter in your custom function as a checkbox that will change value every minutes

=getTime(A2,$A$1)

edit

If you want to manage the trigger to avoid any limitation, you can setup and delete the trigger by the custom menu that will appear at the top right of your spreadsheet

function onOpen() {
  SpreadsheetApp.getUi().createMenu('⇩ M E N U ⇩')
    .addItem(' Trigger setup', 'setTrigger')
    .addItem(' Trigger delete', 'delTrigger')
    .addToUi();
}
function clock(){
  var chk = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Sheet1').getRange('A1')
  chk.setValue(!chk.getValue())
}
function getTime(timeZone) {
  var a = Utilities.formatDate(new Date(), timeZone, 'MM/dd/YYYY hh:mm a');
  return a
}
function setTrigger() {
  myTriggerSetup('clock')
}
function delTrigger() {
  myTriggerDelete('clock')
}
function myTriggerSetup(nom) {
  if(!isTrigger(nom)) {
    ScriptApp.newTrigger(nom)
      .timeBased()
      .everyMinutes(1)
      .create();  
  }
}
function myTriggerDelete(nom){
     deleteTriggersByName(nom);
}
function deleteTriggersByName(name){
var triggers = ScriptApp.getProjectTriggers();
for (var i = 0; i < triggers.length; i++){ 
    if (triggers[i].getHandlerFunction().indexOf(name) != -1) 
    {
      ScriptApp.deleteTrigger(triggers[i]);
    }
}}
function isTrigger(funcName) {
     var r=false;
     if(funcName) {
       var allTriggers=ScriptApp.getProjectTriggers();
       var allHandlers=[];
       for(var i=0;i<allTriggers.length;i++) {
         allHandlers.push(allTriggers[i].getHandlerFunction());
       }
       if(allHandlers.indexOf(funcName)>-1) {
         r=true;
       }
     }
     return r;
}