Given :
Below is the form that user must enter and the top right is a button which allows user to navigate to another screen.

Goal: the top right button is disabled until the user has input all of the required fields. Once the user has input all required fields, the button will be enabled and user will be allows to press it allowing navigation to next screen
Question:how can I achieve this task using thread in iphone.
Please help if you have any clues for this
Thanks
PS: I apology for unclear question at the beginning. I have just updated the question.
UIButton inherits from UIControl
Simply use the button.enabled property.
http://developer.apple.com/library/ios/#documentation/uikit/reference/UIControl_Class/Reference/Reference.html#//apple_ref/occ/instp/UIControl/state