Excel 2007 : Calculate years, months, day

hi guys! good morning/eve.....! im a new member and i want really your help...i have a problem here.

example in:
full date in A1. example 1-jan-11 and in b2=i want in B1 add 10 years but (i have the formula) if B2 is blank i want to change it to "-" or any char until i fill up the A1.


1-Jan-11 expired: 1-Jan-21
but if i delete the date in A1 here is the result

_______________ expired: 31-Dec-09 <-- i want this to change "-" or any word until i fill up the A1...hope you guys get my problem.
this is the formula that i use:
=EDATE(A1,120)