Question regarding dynamically updating a button on a set of modals

Hello everyone, I'm currently working on a project where I'm trying to update the text of a button on a set of modals. The problem I am running into is that with the custom code option in Target, the script runs in the head of the document, and I have not been able to get a click event to work to perform the change when the modal is opened. Has anyone performed a similar test or function in target? I can go through and update each modal with the visual editor, but I'm concerned that this will affect the page loading time. Any suggestions would be greatly appreciated.