关于随机数的Excel 2007问题

In cell A1:A50 i have random numbers geberated by formula ( from 0 to 20), now what ever i do these numbers keeps on changing all the time, so i want to know the formula which will shuffle these random numbers automaticallly till the series whcich have got 5-12-19 in a row will appear. I would really appriciate if some one can help me out of this problem...ThanksIn cell A1:A50 i have random numbers geberated