Run Js Script Inside A Frame - Simple "fill Form" Function For A Specific Page

I am creating a simple "fill form" function for a specific page. The function will fill the form and click submit. after this a second form appears which needs to get filled and also send a click to submit button.

Unfortunately when i append the script dynamically to a page, when the page gets refreshed,after the first submit click, the script stops executing and therefore the second form does not get filled at all.

I searched and found out that if I append the script to an independent frame it will continue executing.

Note that the original pages do not have any frames. so I must somehow create a frame on top, append the script and run it.