osTicket v1.9.12 staff interface edit

We are using osTicket v1 1.9.12 in the staff view ticket interface we create a javascript variable with text from a third party system. We need to inject that text in the textbox at the press of a button. There will be multiple buttons on the page with different text. We will add them later. You need to write the code to inject the text into the text box. We will pass the text to your code via javascript.