I highly recommend you use Froggie's mTwitchNormalizer project :
http://hawkee.com/snippet/16487/ Using these modules you can call for $msgtags in your text events. This returns a line similar to:
color=#FF6BD8;display-name=Nillens;emotes=9:0-1;subscriber=1;turbo=0;user-type=mod
You can either check for subscriber=1 isin $msgtags or you can try to fiddle out the subscriber=1 by tokenizing the string by ; and checking wether subscriber = 1 or = 0