Customer Order Status form in RTC

I’m working on an RTC conversion project - there is a base NAV form 10025. It’s also a page although it looks terrible in the RTC out of the box.

Big problem - this entire form is tied to the Customer table. In the 2009 Classic Client, the “No.” field is read only, however you can bring up the Customer list to select a different customer which changes the record for the entire form.

In RTC, this “lookup” list element is not present. The only way to navigate to a different Customer record is by using the “Actions > Next” and “Actions > Previous” buttons.

This is just not going to work - how do I convert the Customer number field in the Page to be a selection for the current page record?