CEdit or CComboBox

I have a dialog. I want to put either a CEdit or a CComboBox in it.

That is, I want an edit box when I create the dialog this time. The next time I create it, I want it to be a combo box instead.

I could put two controls on top of each other, and just make one visible, but I hate doing that.

Is there a better way?

You can create one you need at the runtime.
I do not think there is anything wrong with showing stacked controls that you add in resource editor.