Pull to refresh normal expressions (non list)

Hi I am trying to refresh a field that is not in a list.

I have a screen that displays a balance and the balance should be refreshed after amount has been deducted by an operation in another screen.

I have a transaction history as well that gets updated using the refresh function but the balance doesnt get updated.

My code is as follows:

< h4 href="#/tab/dash/">Your account balance is: {{balance | currency}}< /h4>

This expression needs to be updated every time the user leaves the tab and comes back.