I am not sure you can use the explicit array approach (Rx[26] = "," etc) as the NMEA sentences are variable length and what might be a comma this time may not be a comma when the field data changes.

I posted code to decode/parse GPS sentences a year or two back.
Have a look at:-

http://www.picbasic.co.uk/forum/show...ghlight=parser

HTH
BrianT