Form select chain event

Form select chain event

Hi, i have 3 select boxes which contain categories, sub categories and a further sub category. Is there anyway i can do a chain event so the last 2 are disabled but the first one is enabled.

Upon selecting a category in the first form select the second form select becomes available. Then once the 2nd form select has been selected this makes the last one become available.

I have created a fiddle of my select boxes -  http://jsfiddle.net/L4t83nvz/

Any help with this matter would be greatly appreciated.