User defined drop down lists

Hi would anyone have any ideas or links about how I could do the following - e.g. If I need info provided by a user on a form about their previous job types, how do I let the user decide how many jobs they have had i.e. input job 1 type from drop down then click a button that provides another drop down list for job type 2 and collect all this info.
I am ok on drop down lists just don’t know how I could insert a button to call up job 2, 3… drop downs.
Thanks
Brendan

You would need to make your dropdowns disabled by default in the properties panel , the create an onClick() function for your button that will contain an enable() function for these dropdowns