How to convert negative numbers to positive

No need to write the column name before the equal sign. The column name is specified in the action settings in the sidebar. You can write

= 0 - [netsales]

or even

 - [netsales]

The equal sign is not necessary either.

That works too:

[netsales] * -1

An example is attached.

inverse.morph (2.2 KB)