webui input requirement

i have two input fields like first name and last name and have result field like full name and display button...............

the result field initialy disabled........

wen click display button the fullname should be displyed in result field .. and wen i click on displayed field the result field should be enabled.....

so how to read input values from first name and last name................. means what are the methods to read values from input field.......

please solve this scenario.........................