If you can do that then you are most of the way there. The simple way is to create a loop. First write out your line, delay a bit, then write out a blank line, delay a bit then start the loop all over again.
The delay does not need to be any thing fancy. It can be a for loop.
The right way to do it is to setup a timer. The text you write to the lcd would be written to a string variable instead. The timer interrupt routine would have a flag called bWriteBlank. It would be set to false by default. If false the timer interrupt writes the string to the LCD if true it writes a blank line.
Give it a try yourself first. If you get stuck I will see what I can do about writing the code for you. But you should try yourself first.
Try the first suggestion I had first then you can move on to the more complicated timer interrupt.