How do I create a permanent field calculation in an AGOL feature layer?

[AshleyThornton]

I have create a map to use in Collector for ArcGIS for the fire department. After using it they have a request: Once they input values for Field A and Field B, they want Field C to calculate a solution using Fields A and B.

I have used the calculate field function in AGOL (ex. Field C = Field A + Field B). However, the field will not 'remember' this calculation. I want the field calculation to stay in that field so that each time I or another user opens the map and inputs the data for A and B, it will auto-populate the value for C.  Is there a way to NOT have to run a field calculation each time I open the map?

[PayneTodd]

In dashboards I was able to hack the table view and display a calculated expression.  The key was to add a field that was not being displayed in the table (like OBJECTID) Then update the label in the Header  section for me it was updated to STATUS.  Then in the Values section return a calculation for the status as the display text.  DEFINATELY A HACK.  It would be nice to add a calculated field to the hosted feature layer directly, kinda like a computed column in SQL. or perhaps in a view of the layer.

OBJECTID: {

      displayText : alarmStatus,

      textColor: 'Red',

      backgroundColor: alarmColor,

      textAlign: 'right',

      iconName: '',

      iconAlign: '',

      iconColor: '',

      iconOutlineColor: ''

    },