Build an Intel HEX interpreter for Arduino

I need a small script for Arduino in which it can receive and transmit string data from/to the serial port and interprets the received data (convert to from HEX pairs to ASCII) and encapsulate string data from ASCII to HEX and be transmitted to the serial port. It is very simple to the ones who knows how to low level coding. I've done the first part but was unable to do the second. For this job I want you to write it both though. Instructions on how to convert/interpret Intel HEX can easily be found online. The ONLY difference from the actual protocol is that I need the different parts of the protocol to be stored in separate variables so I can manipulate them at any time. Please only bid if you have real expertise on this. Don't waste my time, please.