Custom Tab Phone Dropdown

Hi all,

I'm trying to create a custom customer tab that among other things has a dropdown containing the patrons various phone numbers and I have a slight problem I hope I can get some help with.
I've been working under the assumption this would be a dependent dropdown with the dependency being customer_no so I have a INT column that uses a data window to select phone_no(data column) & phone(display column) with a retrieval argument of customer_no from t_phone.
SELECT
T_PHONE.phone_no,
T_PHONE.phone
FROM T_PHONE 
WHERE T_PHONE.customer_no = :customer_no

The tag on the column references my text column and customer_no
{phone_desc, customer_no}

The problem I'm seeing is that the dropdown is not populating unless I save the row and reload the patrons account and if I do that I now get the list of phone numbers. I have the auto-retrieve unchecked as per normal dependent dropdown instructions.

Any ideas out there on what I'm missing?

Thanks!