Designer - copy field - then make readonly

Hi All,

In the awesome V10 you can copy a field in Designer. Select the field, then click "create copy". I'm using this to show the same field in multiple tabs.

Does anyone know how to set the field to makereadOnly in pageload?? Only the original field is being set to readonly by this method:

var c1= Runner.getControl(pageid,'displayname'); 
c1.makeReadonly();

Thanks for your help.