Alter a wordpress form

Hi, I have a simple job for someone who knows what they are doing. I have 2 wordpress forms which uses custom taxonomies and I had some custom code written for me. The categories are divided into three level categories like this -Parent --Child ---Grandchild This works perfectly. Now I need an additional textbox with an autocomplete that autosuggets ONLY the grandchild categories after the user has typed in three characters. When the user selects a category in the autosuggest,then the three level dropbox which is already working should then automatically complete the child and parent drop boxes. This needs to be done on two forms but implementing it on the second form should be a very quick job because the forms are basically identical. I am looking for someone who I can contact for ongoing work so if this project goes smoothly,there will be lots more work in the future.