how to use two calculated columns in same select statement

Hi how to rewrite the following question, here 'history' table, used_life int datatype, ul_units varchar, ul_units may contain data of firings, starts, landings, how to use two calculated columns in same select statements

here user will enter history of flights in hh and mm in two texboxes i am converting into minutes and storing, it is a simple select if it is like this

select used_life/60 as hrs,used_life%60 as mns 

but how to write this

select
case when (used_life>=60 and ul_units='HH:MM') 
     then (used_life/60) 
     else used_life end as used_life_hrs
case
when (used_life>=60 and ul_units='HH:MM')  
     then (used_life%60)  
     else used_life end as used_life_hrs
from history 

here i have to do all this conversion only when the ul_units are HH:MM and used_life>=60 else i have to print the data as it is

above query giving syntax error

can anyone help

Thanks in Advance