Hi Evan,

Here is an example:

First, make sure the drop-down field choices/values all start with currency code as shown in field options (like "USD - US Dollar($)"). This will be used to find choice symbol. Add CSS class "currencyFormat" to the drop-down field.

Then, apply the following script

$(document).ready(function(){
  var currencyFormat = '';
  //When currency format is changed, update currency fields
  $('.currencyFormat select').change(function(){
    currencyFormat = $('.currencyFormat select').val().substring(0,3);
    UpdateCurrency();
  });
  //If form is read only, get currency format from text and update fields
  if ($('.currencyFormat .ro')) {
    currencyFormat = $('.currencyFormat .ro').text().substring(0,3);
    UpdateCurrency();
  }
  function UpdateCurrency()
  {
    if (currencyFormat) {
  	  $('input.currency').attr('currencyformat', currencyFormat);
      //Update field symbol
      $('span.margin-end').each(function () {
            currency = _.find(currency_list, { 'code': currencyFormat});
            $(this).text(currency['symbol']);
		});
    }
  }
})

p.s. I tried to update currency decimal place as well but it didn't work as expected. So currency decimal place could not be changed with above code.