How to build a dropdown like a date selector

I have a field in the bubble that I need to provide a drop down similar to the date picker.

Assuming that the proposed drop down is in HTML and the javacsript/jquery code is available, how do I:

1. detect and activate the dropdown when the field in the bubble is selected.

2. structure/create/display the dropdown and handle input from the field and put data into the field.

Any thougnts, or better yet, examples.

Regards,
Jim