Stop text input for item property in relationship grid

Hello,

Is it possible to stop users from selecting an item for a item property using text input in something like the part number property of the product model relationship item? I've added a filter to the OnSearchDialog event of the property to limit the choices, but since it only triggers when the … button is used to open a dialog, I can still input any part number through text.

Is there any way to stop this text input or do I have to make a method that checks the property OnCellChange to verify the selected value?

/Rick