There's no direct scripting way to do what you want. mIRC scripting is single-threaded, which means that nothing else can run while another script is processing. The only way to use any kind of multi-threading in mIRC scripting is with the identifiers $comcall() and $dllcall(). It would be pretty easy for someone with a bit of C/C++/Delphi/lower-level-language-of-your-choice to make a DLL with a CRC function. Perhaps there's a way to do compute CRC's with COM aswell, but I don't know.
