To Provide Custom Cells and Create Placeholder Fields

Set the MS_DGNLIBLIST configuration variable to the location of your DGNLib or Cell file.
Select the Place Text tool.
Click the Insert Field icon and select the Place Holder Link Properties field type.
If you want to create a place holder link field pointing to a property of a drawing boundary, select a DGN file that contains a drawing boundary.
In the Link Target dialog, select a drawing boundary.
In the Fields Editor dialog, select a property.
Note that the placeholder field uses the selected drawing boundary only as a template to display properties. After it is placed, it does not point to that drawing boundary.