Could you please help wit the following problem;

1. I have a record keeping app called Concatenate App.
It's designed to keep notes of conversations or other interactions that we have with customers.
Please access it at  https://creator.zoho.com/zoho_zubin/concatenate-app/

2. It has one form called "Concatenate Form".

3. Each one of the records in this form relates to a customer's file.

4. The form has 3 fields:

a) All File Notes - this is the field which I would to display the combined/concatenated file notes we have about a particular file.

b) Existing File Notes - this filed has a collection of past and prior file notes that we have about the file.

c) New Note - this filed is where I would like to add new files notes, which are then automatically added to the "All File Notes" field.

5. What I would like to achieve is being able to:

- Type a new file note into "New Note" filed, click "update" and then that file note is added to the "All File Notes" field, where it is combined with file notes from "Existing File Notes".

- Then, when I need to add another file note, the "New Note" field is blank, I can type another note and it is added to the "All File Notes" field.

6. I've tried doing this with a simple concatenate function but the result is not suitable.

For example:

Field "Existing File Notes" has the following content: 
"these are all the existing file notes that should not be editable"

Field " New Note" has the following content:

"test new note. add again".

On load I have a script running:

1. input.All_File_Notes = input.Existing_File_Notes + "\n" + today + " " + zoho.loginuserid + " " + "added:" + "\n" + input.New_Note;

The end result is that Field "All File Notes" produces the following content:
"these are all the existing file notes that should not be editable

09-Aug-2015 zubin@statelaw.com.au added:

test new note. add again".

The problem is that that I can't add any more new file notes after that.
If I delete the "test new note. add again" content from Field " New Note" and replace it with other content, then this content will be gone from "All File Notes".

7. Could you please tell me how I can program these fields so that I can keep adding new file notes about my customers?

Thank you so much!!!!!!