Simple IF statement help required

[dwilkinson12]

=IF($C1<=EDATE(TODAY(), -11),"r","a") the following formula works and displays the correct letter r or a depending on a date which is in the referenced cell. If I wanted to put this in lots of different cells that don't have a date in it's respective referenced cell how could I modify the code to show nothing in stead of the false value if there is no data in the referenced cell?

Thanks
Daniel

[martindwilson]

=IF($C1="","",IF($C1<=EDATE(TODAY(), -11),"r","a"))
=IF(ISNUMBER($C1),IF($C1<=EDATE(TODAY(),-11),"r","a"),"")

[zumbalj]

=IF($C1="","",IF($C1<=EDATE(TODAY(), -11),"r","a"))

[dwilkinson12]

Thanks for your help guys...