It seems neither your .msg nor your .dat were correct.
The comand that I have used are
thmsg c13 st01a.txt > st01a.msg
Then
thdat c13 th13e.dat > st01a.msg
Don't put a > to rebuild the files. What the above is saying is, "do 'thmsg c13 st01a.txt' (which will give an error since it's missing a file), then put whatever that says in st01a.msg" Instead, do this:
thmsg c13 st01a.txt st01a.msgAs for thdat, you will have to include the filename of every file that you've extracted from the .dat and not just the one files you've modified. Taking out the > from your command, you'd be telling thdat to make a .dat file with just one file contained within it: st01a.msg. Instead do this:
thdat c13 th13e.dat "file1.ext" "file2.ext" "file3.ext" "so on..."It may take a little while to type up everything so you should keep the command in a file to copy-paste for future modifications. Alternatively, you could write yourself a batch file, though if you don't know what that is don't worry about it. Copy-pasting it will come out the same, pretty much.