Angular 2 two way data bindings and tabs

I am working with angular2 and ionic2. I have two tabs. the first one contains a calculable field.
i do the calculation in a shared component.

the second tabs contains the discount of this finalAmount. i get the input and i do the calculation on the second tabs.

so if i go back to the first tabs i notice that the final Amount doesn’t change. it will display the change only if i go back to the previous component like home page. i have this idea to work with the custom two way data bindings but i don’t think that will resolve my problem because i can’t work with another two way data binding in the same input.

tabs 1 : image

tabs2 : image

how can i resolve it
thank you in advance

thank you guys. i drop all my work and i use the two custom way data bindings and it works.
the shared component or pass data between tabs doesn’t work with me