Using lookup tables in Ensemble/Routing Rule/DTL

Does anyone have experience in creating a Business Routing Rule using Exists function?

I've used the comma delimited 'In' function, but I would like more manageability. Entering and remove items from a look up table would be much easier to manage then changing the comma delimited string.

Messages go to error state.

Any help would be appreciated.

This is my first post, so if I am doing anything wrong please let me know.