Changing the label of the extension field according to the log-in user country

Hi everyone,

I would like to change the extension field label according to the log-in user country.

I added the extension field in the standard BO. And then I write code to get the log-in user country.

I try to write the sap ruby script code in the label of the extension field in the UI designer.

But the following error occurs.

And all of the property editor is read-only mode.

I would like to know if there any other way to change the label occasionally.

Thanks,

Thu Thu