Save button in Exhibit builder admin page


I would like to call a function in my custom.php that will add a new data to theme-option link in exhibit builder table in db once the user click on Save button in exhibit builder form in admin site.

I created the function in custom.php that will save the data to the theme_option variable but I was looking at the exhibit builder plugin to see where I can do this call for the function.


I decided to Add more about what I am trying to achieve.

I do need to attach an image to each exhibits created in the browse page. So I thought to get the image from the first item included in the exhibit and display it. but I would like also to save this image with each exhibits created and I thought the best place to save it in is the theme_option serialized data.
I created the code that get the image and save it in the serialized data theme-option. This code is created in a function in a custom.php file. but When I tried to call this function after an exhibit created it gave me an error bc the Exhibit builder does not see the custom.php

I was wonder how I can perform this without missing up with the code in the exhibit builder. is there a filter for admin site or any other ideas appreciated.