How do I prefill a dropdown list and have another dropdown automatically populate info based on the first value.

Sorry, couldn't figure out an easier way to word this.

For example, I have a PDF for fishermen to count catches. There is a dropdown list for VESSELNAME. If the user selects their vessel name, I want the other dropdowns like vessel ID (REG_ID_CG) to prepopulate with the related unique info. Here is an excerpt of the CSV with sample data I received:

Do I need to format the CSV into an XML schema? How would I connect at least these two dropdown fields?

Thanks,

Justin

*edit*

Here is what the XML looks like when converted from CSV. Am I able to use it in this format?:

<?xml version="1.0" encoding="UTF-8" ?>

<root>

    <0>

        <REG_ID_CG>1346585</REG_ID_CG>

        <VESSEL_NAME>JVESSEL</VESSEL_NAME>

        <GEARDESCRIPTION>TROLL/JIG</GEARDESCRIPTION>

    </0>