Filter relation ticklist widget without a parent relationship

Hi,

We’re trying to use a relation ticklist widget in one of our forms, however we have a lot of records that the base record can be related to.

I know that you can create a drilldown by choosing a parent relationship for the selector path, but I was wondering if there was a way to do this without having to create a parent relationship, such as using a property from the base object?

Thanks,
Ewan