For example, if I have

```
=INDEX(B1:B100000,MATCH("my_val",A1:A100000,0))
```

in a cell, how can I change that to

```
=INDEX(C1:C100000,MATCH("my_val",A1:A100000,0))
```

without triggering the (slow) Index-Match?

(I've already set calculations to manual, but Excel still recalculates a formula entered or modified by hand.)