easiest way to get AUX functionality on 2001 325ci ?

what would be the easiest or the most cost efficient way to get AUX functionality on a 2001 325ci? i have the Blaupunkt head unit with the CD button. is it true that i must upgrade to a newer head unit say 09/02 or later in order to get the AUX input working?



any info or help will be much appreciated! thanks!