JQuery Cascading Dropdowns with PHP/MySQL

I need to have a series of four dropdowns that are all populated using PHP from a MySQL database and as one is selected the next are filtered according to the option on the first one. Details: Dropdowns: Group, Country, Region, City When a Group is selected, the code checks against the database to see what Members are in that Group and then filters the contents of Country + Region + City dropdowns to only show the Countries/Region/Cities which have Members from that Group. When Group + Country are selected, the code checks the database for all Members that are BOTH part of the Group and have offices in that country and then filters the contents of the Region + City dropdowns to only show Regions and Cities which have Members from those filters Same thing when a Region is selected - Cities dropdown is populated with only cities that have Members in them with those filters If a City is selected before a Region or a Region before a Country, no change should take place in the previous dropdowns until they are adjusted. Table structure: Required MySQL table structure includes a Groups, Members, and Member_Group_Link table with the primary fields being: Group table: group_id, group_name Members table: member_id, member_country, member_region, member_city Member_Group_Link table: link_id, link_group_id, link_member_id Example: Member X is a part of Group A and has 2 Offices in Buffalo, New York, USA and one in London, England Member Y is a part of Group A and has an office in Rochester, New York, USA and one in Miami, Florida, USA Member Z is a part of Group A and has an office in Toronto, Ontario, Canada and one in Sydney, Australia The User selects Group A from the first dropdown. The other three dropdowns show 1) Country: Australia/Canada/England/USA 2) Region: Florida/New York/Ontario and 3) City: Buffalo/London/Miami/Sydney/Toronto/Rochester The User then selects USA as the country from the second [country] dropdown. The other two dropdowns show 1) Region: Florida/New York and 2) City: Buffalo/Miami/Rochester The User then selects New York as the region from the third [region] dropdown. The final dropdown shows 1) City: Buffalo/Rochester Ideal Deadline: 24-48 hours for full completion