Excel或Google表格：根据变量的变化返回值

I have two columns with variables A to E. I would like to calculate the change in those values. For example, if A1 is "A" and A2 is "D" the change is +3. If A1 is "D" and A2 is "A" the change is -3. What function can I use to calculate this?I have two columns with variables A to E. I wou