Morning

I have a spreadsheet where I have pupil target grades and achieved grades. I would like to convert the 'letter grade' into a 'number grade' showing the difference between achievement.

For instance:
  • Target grades go from A* to D
  • Achieved grades go from A* to C
  • If a pupil has a target of a D but achieves a grade A he will be = 3 grades aboove this target
  • One more example, pupil had a target of an A, but achieved a C, so would = -2 below target

Any ideas?

Thanks