Ok i have a number grid that is 10 across and ten down. with numbers running from 1 to 100 or more. A box is drawn on this grid and i need to find the product of the top left number and the bottem right number in this box. I must do the same with the top right and bottem left numbers. I then have to calculate the differnce between these two numbers. I have to do this until i can find a formulea which i have maneged to do for the even boxes e.g 2x2 3x3 4x4. The formulea I have found that works is the following 10 (n-1)2 (squared cant find chacter on keyboard) Now my problem is when I try and find the formulea on the odd size grid boxes e.g 3x2, 4x3, 5x4 Anybody know of a forulea to work out what the next grid box differnce would be for example the differnce in a 7x7 grid is 300 what formulea would i use to find out the differnce in a 8x7 grid. Any help would be most appreciated im rubbish at maths and this is driving me mental.