The normal way to support blink is to make a function that is called from your main program loop. This function would watch a timer driven count byte that registers the passage of each 1/2 second. At the beginning of the first half second the blinking portion of the LCD screen is written with the normal display characters. At the beginning of the next 1/2 second time this area is written to space characters. This process continues on an on till the blinking process is supposed to stop. At the stopping time a flag variable is cleared which disables the blinking function of the subroutine.

I hope that gives you an idea,,,
Michael Karas