Relation N:N

Hello to all,

I created a small mask including a Relation NN, the program automatically manages everything and that’s fine.

my need but it would be when I click one of the flags of the relation Checkbox I would like to trigger an Ajax event so maybe you can make of things before having to record in the related table.

Let me give an example

I need to calculate a total price that is given by the base price in the mask + each active check box that you should add to the base price, the latter amounts fetch them from an external table (Extra Prices) with various prices.
Finally it is possible to identify those individuals (fields / checkboxes) before you record in the related table?

Do you have some advice about it?
hello to all