Dear all; How are you? I have a problem to find a checkbox value in a form. Here is the page I am working on. http://www.hyalina.com/event/building-and-updating-social-accounting-matrix-... In the bottom of page, there is collapsed form ("Sign up for Building and Updating a Social Accounting Matrix"). Inside, there is "Data" section. Inside "Data" section, I added a checkbox (Supply and Use Tables/Input-Output Table). What I want to do is that if the checkbox is checked, then one textfield (year) is shown. If unchecked, then one textfield (year) is removed. I can get some data from $_POST. (See the above link with DSM ($_POST or See the attached). I can see the element (data1_checkbox) of the form, but I can not find the value of the checkbox (checked or not checked). Do you know how to find the value? I guess that I might get the value from " $form_state['values'][data1_checkbox] " but I don't know how to get the $form_state from $form.. Could you help me out? Thanks so much!! Best Regards, Soonho