cant understand an expression in qeury

[raffi]

hello theres a query and in the query a field which has the following expression written under, its actually fully operational and working 100% but im having hard time understandind how its doing what its doing, how can this one line be responsible for both adding and subtracting ? ...

Actual Quantity: IIf([Transaction Types].[Add/Remove]="Addition",[Inventory Transactions]!Quantity,-([Inventory Transactions]!Quantity))

ok so if the table name "transaction type", field name "add/remove" is equal to "addition", then table name "inventory transactions" field name "quantity" will be deducted by ? itself ? huh ?....

[orange]

Here is definition, syntax and example of IIF()

[pbaldy]

It returns the quantity as positive or negative as appropriate to the type. That would enable it to be summed or simply displayed more visually.