Buddypress plugin

Hi all,

I am using Buddypress Plugin Version 1.5.5, I am trying to create a Custom Registration form with the help of Profile Fields. I created required fields , But i have used drop down select box where all my categories are set; Where, user can select the options provided.

My Query is I have given all possible Category, IN-CASE if user wont find the option from the drop-down select box, I have given a 'Others' option. Now when user select a 'Others' option, "I want a text box to pop up as the user select the 'Others' option. I am very poor in coding(programming) point of view. It will be great if some one suggest me with a plugin.

Please let me know how to resolve this issue.