Answer
No, in ArcGIS Online, it is not possible to automate field calculations. As an alternative, use ArcGIS Pro.
- In ArcGIS Pro, log in to the ArcGIS Online organization account.
- On the top ribbon, click the View tab. In the Windows group, click the Catalog Pane icon.
- In the Catalog pane, click the Portal tab, and search the desired layer. Right-click the layer, and click Add To Current Map.
- Create a model using ModelBuilder. Refer to ArcGIS Pro: Use ModelBuilder.
- On the top ribbon, click the Analysis tab > Tools.
- In the Geoprocessing pane, search for the Calculate Field (Data Management Tools) tool. Right-click the tool, and select Add To Model.
- Double-click the Calculate Field tool in the model to open the Calculate Field pop-up. In Parameters, select the input table and field name for the Input Table and Field Name (Existing or New) sections.
- Select the field type for the calculations in the Field Type box.
- Select the expression type in the Expression Type box, and fill in the expression box with the desired calculation. Click OK.
- Click Save.
- In the Catalog pane, click the Project tab. Expand Folders, and double-click the model.
- In the Geoprocessing pane, in Parameters, select the desired parameter. Click the Run button drop-down menu, and select Schedule.
- In the Schedule: Model window, specify a name in Task Name, and select the desired recurrence time from the Recurrence drop-down menu.
- Specify a starting time in the Begins On section, recurrence expiration, and ending time in the Ends On section to automate field calculations. Click OK.
- Click Run.