Hi Armond,
There's no easy way to do this. But it can be done.
What I would do is set ButtonDisplayStyle to Always. Then use a CreationFilter to remove the ButtonUIElement from the cell under certain conditions. It's a big tricky, but I'm sure it can be done.
If you are not familiar with CreationFilter, they are really powerful and worth the effort to learn. Check out the Infragistics Knowledge Base for articles and sample CreationFilters. Also, get the Infragistics UIElementViewer Utility. It's a big help when working with UIElements.