If FullTRFText is defined as a string and Line Input reads a string
terminated with an end-line of some sort, then Excel is probably quite
properly ignoring nulls.

I think that there's a "get" call that will read the file in smaller chunks.
If you need to read it byte by byte, then you probably need to use Get to
read into a character/byte variable or possibly a character/byte array.

(Sorry for the vague reply - a quick Google search wasn't very informative.)