You can assign a referenced reference at run-time via PROP:Use. Don’t try to use a reference in the window definition.
If you can do that, it’s a lot safer than trying to get to the use variable of the control itself.
If you know the data type, you can use something like this example attached to this message How can you dynamically disable fields on a form at runtime? - #5 by jslarve That will get you the address. If you know the data type, you can assign a reference to it.