How to change attachment field when item in list box is clicked

I have a form set up as follows:

A combobox called “categories”


A listbox called “moldnames”


An attachment field called “moldpic”

They all pull from a table called “Outside Master List” which contains the following columns:

ID, MoldName, Category, BoxNumber, Attachment

Selecting a category from the combobox(categories) changes the contents of the listbox(moldnames), That’s all working fine.

But I have no idea how to make the attachment field(moldpic) display the image that corresponds to the item that is clicked in the listbox.

How to change attachment field when item in list box is clicked