I have a table which looks like this:

```
+---------+--------+-------+
|categ    |decrea  |lost   |
|---------|--------|-------+
|A        |1500    |20     |
|B        |1500    |40     |
|C        |1500    |60     |
+---------+--------+-------+

```

And I want to change the decrea values so that each value is equal to decrea minus the accumulated losses. So the result would look like :

```
+---------+---------------+-------+
|categ    |decrea         |lost   |
|---------|---------------|-------+
|A        |1500-20        |20     |
|B        |1500-(20+40)   |40     |
|C        |1500-(20+40+60)|60     |
+---------+--------+------+-------+

```

Anay help please ?