im trying to reproduce following effect.  

I have two input elements on form: 
class=time and id=timefrom
class=time and id=timeto 

i want to hide/remove this elements create select element with hours and minutes example  

00:00  

00:30  

01:00  

01:30  

02:00  

...

Second element should be dynamic  

for example selecting in first element 01:00 should cause  

change values in second element for example  

01:30 (30 min)  

02:00 (1h)  

02:30 (1h 30 min)  

i didn't find any plugin for this im trying reproduce 
this effect but with no luck :(
help