value added ks4/5

[jabjab]

hi im trying to work out value added which is how many grade above and below of your target grade you are working at. i have this working for ks3 and it works for key stage 4/5 however when the current working level is a U and the target grade is an A it shows a value of -20 which is wrong as i need it to show -5. i am using the code function which works for all other grades which are A,B,C,D,E,F but wont work for A* or U grades. can anyone help me with this problem

[arthurbr]

Would you care to elaborate ?
Nice smileys !

[jabjab]

so basically i have a system which i have created which has student data. In this data it contains a students target grade. a students target grade is the grade they are expected to get at the end of the school year. to work out value added you need to take away the target grade away from the current working level. In key stage 4 and 5 the grades are A*,A,B,C,D,E,F and U. These are not numerical hence why i was using the code function to chnage them into a number which is fine up to a point where i need to find the value added for grades A* and U. so if a Student was working at and A* and predicted a B value added would be +2 and if someones current working level was a U and target was a C then value added would be -4.