DataGrid - Collumn.LinkedObject property and UDO

He all,

I have a new question. I'm a form with a grid. The grid contains ItemCode, ItemName, CardCode, CardName and others columns with any values. I was linked ItemCode with de ObjectType 4, there is okay. When the column has text, appears a row and clicking opens the form 150.

Another columns points to a User Objects (I have MasterData type and Document Type) and I try to make the same behaivor. Unfortunately the form ignore these asociation and not shows the arrow. The question are, this cannot be done?

Thanks in advance