Reusing property editors for Blend 4

I have a custom silverlight control, which exposes a property with DataGridLength type. Now I want that property to have the same editor as a common DataGridColumn's Width prop开发者_如何学Certy, with the combobox and everything, like this:

instead, I only get a simple TextBox, with "Auto" written in, with no way to set to SizeToCells and so on.

I assume I need a DesignTime attribute, but none of the ones I found in ComponentModel namespace even came close...

I guess you just have to create an Enum with the all the values autorized (Pixels, SizeToCells, etc ...), you that Enum as the type of your property DataGridLength and then, in the code of your control, take the corresponding action regarding the value sent.