Return values from Operation Multiselect ListBoxProp


Does anybody know if it is possible to retrieve the values selected in an operation multiselect listbox and return them as a concatstr in a feature property?

I am connecting to an ArcSDE graphical data source so am unable to use the listbox as a feature property but would like to emulate that functionality via an operation property instead.

I have successfully used feature properties and sync watchers to drive values in operation properties but am struggling to do it the other way round, or retrieve the multiple values from the list box.

Any pointers on how to achieve this would be gratefully received.

Mny thanks