Export to CSV efficiently? (code review)

I wrote this function to export a list to a generated CSV file.  However the for loop takes hours to run (albeit I am exporting 100,000+ items, but still, the commands that generate these items change things in my project and those only take a few minutes).  I tried to create a 2nd order string buffer because I figured that fprintf to port may have been a bottleneck but this made it run even slower (ran all night and still wasn't done).  Can someone please offer any improvements to this?  I left the previously direct way of export via fprintf commands commented out.

procedure(writeListsToCSV(headerList ListOfLists fileNameSuffix location)
  let((buffer buffer2 comma currentDateTime DateTimeList TimeList year month day time fileName fileHandle lengthHeader)
  ; Get current date and time;;; getCurrentTime() ; => "Jan 26 18:15:18 1993"
    DateTimeList = parseString(getCurrentTime() )
    year = nth(3 DateTimeList)
    month = nth(0 DateTimeList)
    when(month == "Jan" month = "01")
    when(month == "Feb" month = "02")
    when(month == "Mar" month = "03")
    when(month == "Apr" month = "04")
    when(month == "May" month = "05")
    when(month == "Jun" month = "06")
    when(month == "Jul" month = "07")
    when(month == "Aug" month = "08")
    when(month == "Sep" month = "09")
    when(month == "Oct" month = "10")
    when(month == "Nov" month = "11")
    when(month == "Dec" month = "12")
    day = nth(1 DateTimeList)
    time = buildString( parseString( nth(2 DateTimeList) ":") "")

    currentDateTime = buildString( list(year month day time) "_")

    /* I couldn't get this to work, "/" as last character returns "\/" and the compiler hates "\"
    print(getchar(location strlen(location)))
    printf("\n")
    when(not(getchar(location strlen(location)) == "/")
    strcat(location "/")
    )
    */

    ; todo:need to incorporate isReadable(filePath) and getWorkingDir() for better flow
    fileName = strcat(location
                      "/"
                      currentDateTime
                      "_"
                      fileNameSuffix
                      ".csv")

    ; Write the headers
    buffer = strcat(buildString(headerList ",") "\n")

    printf("\nFor loop begins at: %s\n" getCurrentTime())
    lengthHeader = length(headerList) - 1
    ; Write the list values to the file
    for(j 0 length(ListOfLists)-1
        buffer2 = ""
        for(i 0 lengthHeader
            ;print(type(nth(i nth(j ListOfLists)))) ;;if missing values then check possible value type here
            ;printf("\n")

            if(i < lengthHeader then comma = "," else comma = "\n");buffer = strcat(buffer ",") )
            case(type(nth(i nth(j ListOfLists)))
                ('string
                    buffer2 = strcat(buffer2 nth(i nth(j ListOfLists)) comma)
                    ;fprintf(fileHandle nth(i nth(j ListOfLists)))
                )
                ('flonum
                    buffer2 = strcat(buffer2 sprintf(nil "%f" nth(i nth(j ListOfLists))) comma)
                    ;fprintf(fileHandle sprintf(nil "%f" nth(i nth(j ListOfLists))))
                )
                ('list
                    buffer2 = strcat(buffer2 sprintf(nil "%L" nth(i nth(j ListOfLists))) comma)
                    ;fprintf(fileHandle sprintf(nil "%L" nth(i nth(j ListOfLists))))
                )
                ('float
                    buffer2 = strcat(buffer2 sprintf(nil "%f" nth(i nth(j ListOfLists))) comma)
                    ;fprintf(fileHandle sprintf(nil "%f" nth(i nth(j ListOfLists))))
                )
                ('int
                    buffer2 = strcat(buffer2 sprintf(nil "%d" nth(i nth(j ListOfLists))) comma)
                    ;fprintf(fileHandle sprintf(nil "%d" nth(i nth(j ListOfLists))))
                )
                ('fixnum
                    buffer2 = strcat(buffer2 sprintf(nil "%d" nth(i nth(j ListOfLists))) comma)
                    ;fprintf(fileHandle sprintf(nil "%d" nth(i nth(j ListOfLists))))
                )
                ('t
                    buffer2 = strcat(buffer2 sprintf(nil "%s" nth(i nth(j ListOfLists))) comma)
                    ;fprintf(fileHandle sprintf(nil "%s" nth(i nth(j ListOfLists))))
                )
            )
            ;when(i < lengthHeader fprintf(fileHandle ",") )
        )
        buffer = strcat(buffer buffer2)
        ;fprintf(fileHandle "\n")
    )
    printf("\nFor loop ends at: %s\n" getCurrentTime())

    ; Open the file for writing
    fileHandle = outfile(fileName)
    ; Write
    fprintf(fileHandle buffer)
    ; Close the file
    close(fileHandle)
    printf("\nClosed file handle at: %s\n" getCurrentTime())
    printf("\nCSV GENERATED AT: %s\n" fileName)
    )
)