How to Reprice Sales Order Line based on a DFF value

How to Reprice Sales Order Line based on a DFF value.

If i select yes - 1 Modifier should be applied

If i update the selection from Yes to No - Applied modifier should be removed

I have created a custom qualifier which captures this input (as Yes or No) and applies the Modifier - when value is Yes. However, if the update the DFF to No, i want this Modifier to be removed