Formatted text find and replace.

As @femkeblanco said: you need the "Palette" dialog type and it will be best to use Bridgetalk to include the script(s).

Create an action that starts your script. Give the action a shortcut.

Something like this?

RegExp search and replace, keep original text formatting 

I didn't tested your code yet.

 

But why you didn't play with my code snippet and use something like this:

// regex_changeContentsOfWordOrString_RemainFormatting.jsx
// regards pixxxelschubser

var s = /arguments/gi;
var replacer = "other string", result;
var atf = activeDocument.textFrames[0];

while (result = s.exec(atf.contents)) {
    try {
        aCon = atf.characters[result.index];
        aCon.length = result[0].length;
        aCon.contents = replacer;
        } catch (e) {};
    }

 

Try it and have fun

 

By @pixxxelschubser

var w = new Window("dialog");
    w.text = "Replace";
var input = w.add("edittext");
    input.characters = 20;
    input.active = true;
var statictext1 = w.add("statictext");
    statictext1.text = "with";
var output = w.add("edittext");
    output.characters = 20;
var button1 = w.add("button", undefined, "OK");
    button1.onClick = function () {
        var frames = app.activeDocument.textFrames;
        var input1 = new RegExp(input.text, "g");
        for (var i = 0; i < frames.length; i++) {
            var substitute = frames[i].contents.replace(input1, output.text);
            frames[i].contents = substitute;
        }
        w.close();
    };
w.show();