am a teacher and am trying to create a datasheet with childrens levels on it. The levels are in the form of text.

w being the lowest, then 1c, 1b, 1a, then 2c, 2b, 2a and so on upto a level 5a. Each level has a numerical value, w = 3, 1c = 7, 1b = 9, 1a = 11 and so on (increments of 2 each time).

I need to create a formula that works out the difference between the childs grade at the end of the year (column B) from the childs grade at the beginning of the year (Column A) from text form with the answer shown in a numerical form.

I have tried doing the following

=IF(V27="w",3,IF(V27="1c",7,IF(V27="1b",9,IF(V27="1a",11,IF(V27="2c",13,IF(V27="2b",15,IF(V27="2a",1 7,))))))-IF(R27="w",-3,IF(R27="1c",7,IF(R27="1b",9,IF(R27="1a",11,IF(R27="2c",13,IF(R27="2b",15,IF(R27="2a",17,))))))))

but has a limit of 8 entries and i need 15!

Any ideas would be greatly appreciated as i am at a lost cause now

Thanks
Andy