Customizing the metamodel : What you can do with USRPROPS/SAPROPS : Layout capabilities : Grids, list and text boxes : ListOf list boxes
  
ListOf list boxes
A list-of list box provides a list box that enables the user to select one or more from a list of values. The definition referenced must have been defined already in SAPROPS.CFG or USRPROPS.TXT. As new definitions of this type are added to the encyclopedia, the list of choices grows.
Example
DEFINITION "Cost Driver" { LAYOUT { COLS 2 TAB ALIGN OVER } PROPERTY "Description" { EDIT Text LENGTH 500 HELP "Text describing Cost Driver" } PROPERTY "Cost" { EDIT Numeric LENGTH 15 HELP "The cost allocated to the activity by the driver" } }
...
PROPERTY "Activity Cost Pool" { ZOOMABLE EDIT ListOf "Cost Driver" LENGTH 4096 LABEL "Cost Pool" }