Cascading dropdown list functionality needed

[dkruger]

What would be the best way to realize the following functionality as part of the Registration form, amongst others: Have a dropdownlist containing 9 Provinces. Upon selecting a Province, a second dropdown list needs to be populated with a list of Districts belonging to that Province only. Upon selecting a District, a third dropdown list needs to be populated with Cities/Towns within that District only. Upon selecting a City or Town, a forth dropdown list needs to be filled with the Suburbs of that City or Town only, also displaying the Postal Code for that Suburb. All of this information is available in DB tables, and the cascading dropdown lists needs to be ideally populated using an appropriate SQL query, to filter the datasets accordingly - we are talking about 9 Provinces, 52 Districts, over 8,000 Towns, with up to 100 suburbs per Town. Any suggestions will be highly appreciated.

[fasse]

Depending Drop-Downs are not supported within our structure for profile fields.

[dkruger]

I understand, but would it be possible to achieve this by developing a custom plugin ? Would that be the best approach, or do you have any other suggestions ?