Random numbers chosen from a column

Working with Excel, I am generating a random number in a single cell from a list of numbers in a column. I am using =@INDEX(Q2:Q18,RANDBETWEEN(1,COUNTA(Q2:Q18))). I want to repeat this process in the next cells (like a quick-pick in the lotto system) but I don't want the values to repeat themselves from cell to cell. What do I need to add in my code to prevent a value repeating itself in another cell?