How to create a else statement if I pressed radio button widget??

Hello,

I want to change the field according to radio button , If unlimited is checked then membership length field is hide and if specific length is checked then membership length field show two field one for insert number and second for dropdown of day,week,month and year and If fixed date is checked then membership length field show date picker for start date and end date. 

How to create a else statement?

Thanks in advanced