LibreOfficeDev 7.4 Help
jM79E‖Returns the next available file number for opening a file. Use this function to open a file using a file number that is not already in use by a currently open file.
FreeFile
RqGSZ‖Integer
3yGe9‖This function can only be used immediately in front of an Open statement. FreeFile returns the next available file number, but does not reserve it.