Enable ion-navbar button while submitting from modal page

Hi ionites!

I’m working in a new mobile app with Ionic 2, and I’m trying to enable a button located in the ion-navbar while having success submitting from a modal page.
this a screenshot : voiture button ( in the top right ) is in the beginning disabled , i would like enable it while submitting.

Any ideas on how to get this effect?

Thanks in advance!