hi all experts,
I want to know how to write a function for below table in result,
There are two column Rcp and Num.
IF Rcp=A or B and Rcp+1= C or D, then Result = Num(Rcp+1)-Num(Rcp+1)=0,
if Rcp+2 =C or D, then Result = Num(Rcp+2)-Num(Rcp+1)
If Rcp+3 = C or D, then Result = Num(Rcp+3)-Num(Rcp+1)
| Rcp | Num | Result |
A | 1 | NA |
| B | 4 | NA |
| B | 6 | NA |
| C | 7 | 0 |
| C | 9 | 2 |
| D | 10 | 3 |
| C | 12 | 5 |
| A | 2 | NA |
| B | 5 | NA |
