Slight issue with Dynamic Picklists

Slight issue with Dynamic Picklists

Hi, I've only recently been put to work on our company Zoho project, but I have some background with code. A colleague of mine asked if I could do some clean up with his forms and make them a little more user friendly.

Currently, what I'm trying to achieve is a simple (or I thought...) dynamic picklist. I've worked through the example you have put forward within the Creator Help pages, but there must be something I'm missing. It's a shame that I can't start at the beginning, but also trying to figure out what my colleague has done also.

Criteria:
So I have a form labelled "ACCOUNTS", within this form people enter an "ACCOUNT_NAME" (and various other details).
I have a second form labelled "SITE ADDRESS", within this form is a dropdown linked to "ACCOUNT_NAME" in the "ACCOUNTS" form. The user here adds an address to be registered here. Each account could have an unlimited amount of site address'.
Finally I have a "NEW SERVICE REQUEST" form, within this form I want to reduce the amount of options to the user. So the Account dropdown is linked to the "ACCOUNT_NAME", now the user selects a Site Address - This is where I need the dynamic picklist to work and generate only the Site Address' that are linked with the same "ACCOUNT_NAME".

EG:
Account names: A, B, C, D
Site Address: 1, 2, 3, 4, 5, 6, 7
If A is selected, show 1, 2, 3.
If B is selected, show 4.
If C is selected, show 5, 6.
If D is selected, show 7.

Thank you for your time,
Patrick.