Pre-populating dropdown field with data from custom field

I’m not sure if my title made much sense but I will try to explain...

I have embedded a form on my page beneath a loop that could potentially contain 1 – 50 posts (custom posts if that matters).
I am wanting to pre populate a dropdown on the form with the value from a custom field from the posts above. The meta_key required is business_name and I need all of these business name values populated in the dropdown.

I have had a look at this code but I’m not really sure how to use it, it doesn’t really give a ‘complete’ solution for a hack like me.
http://www.gravityhelp.com/documentation/page/Dynamically_Populating_Drop_Down_Fields

Thanks