A way for the admin to add options ( text boxes, combo boxes etc ) to a form.

Question

I want to create an administration option to create text boxes, combo boxes and other stuff that I'm going to give as an option. and make a database for it on-the-fly. I don't know if that make any sense at all. Something like this

type: int, string ( <- in a combo box ), name: ( <- text field to input the name of the option) |add-button|

so the |string|,|text-name| |add| is going to produce the following

text-name: | | ( <- text field ).

I'm writing a Ruby on Rails project and I have to make something like that because we don't know what option every users will want and the administrator of the system is going options for every user, so any ideas, ways of doing this?