convert raw hex string to ASCII

hello,
I've been wrestling with this for a while now and need some help.

I am making a system call to read a serial port as follows:
status = CommRead(Port, Buffer, Size)

Where Port is an integer, Buffer is a String and Size is a Long

I get a string of 20 raw hex values from the device I am reading.
When I put the Buffer String into a cell, only the numbers that are ASCII characters are displayed.
I need to convert the raw hex value to an ASCII set then place the 20 values into 20 different rows.

I've tried indexing into the string, but I always seem to get compile errors. Buffer.Chars(int)
Side note, my version of VB won't let me declare a Char variable.

Thanks for any help you can offer.