thanks guys its working now.
I got one more thing which i'm not able to sort. i'm using the formula F3-TODAY()....where F3 is a date in the future. This works on for the first cell i entered this formula in, but if i want to drag down the formula i get -43141 in the all the other cells, but i want them to remain blank until a value is added in F4, F5, F6.....etc