How to update form field from CUI button in item window command bar?

Hi community,

has anyone of you ever updated a Form field from a CUI button event from the ItemView.ItemCommandBar (=the main toolbar with the Edit/Done/etc. button when a Form is opened)? 

I am right now look for some code sample for this use case, but haven´t found the right one yet.

I want to move some regular buttons from the Form to the ItemCommandBar cause it better fits the use case. 

With regular Form buttons updating Form fields is pretty easy. We can use window.handleItemChange("xyz","newValue") to update the fields.
But we cannot use the same function from a CUI button in the ItemCommandBar.

Does anyone already have a sample Method for this one?

Thanks for any help!

Angela

Edit: thisItem.setProperty("xyz","123"); updates the context item, but it doesn´t do a live update in the Form field. So with the one the new value only appears after the user clicked save. I want to live update the Form with CUI, just like it would do with handleItemChange