Mitchell,
Step one (don't know if this is realy needed....never had the need to use them):
Intall 1 out of 3 available tools, PPC Command Shell, PocketCMD or PocketDOS.
Step two:
Write your dos command to a BAT file and theirafter start this BAT file, e.g.:
fSaveText("\MyFile.bat", "copy invoice.prn COM4:")
ExeRun("\MyFile.bat")
HTH
Merijn