I will appreciate it if who could help how to set an SLX Edit control as the mode of multiple lines and to be able to appear a vertical scrollbar automatically when need?

Have you looked at the memo box control?

Yes, I tried the memo cotrol before. The control can support the mode of multiple lines but the vertical scrollbar doesn't appear after the input gets large enough. Any thoughts?

Make the memo coontrol narrower or shorter as needed.....non way to do this on the fly that I'm aware of.....

you could try changing the width and height on the fly and then a windows process messages.....