In design-time, can I get a list of controls on a form using a script in the memberdata editor?

For example, for a given property on a class I want to add some code to the memberdata to give the user a list of textbox controls on the form being modified (example only) to select from.

ASELOBJ() and the like depend on the control being selected or moused-over etc. In this case the form is open in the designer, but the mouse is the property-sheet.