Dataset filter

Hi, I tried finding an answer in the posted cases but with no luck.
I have an input box connected to a W&W dataset where the user has to input a value. This field is connected to the “quantity reserved” field. I would like to constraint this input with a simple lower or equal to the number in the “quantity available” field.

So I tried to build the dataset with the filters like
“quantity reserved” is < or = “quantity available”

The idea is to prevent one from reserving 5 units of an article when only 2 are available…
Any idea?