Populating Distinct Drop-down values in Input Form

Hello Folks,

We have a schema with a link established to mapping table for populating drop-down values of a particular field. However, this schema does contain Non-Unique data and my requirement here is to populate / show only DISTINCT drop-down values on the Input Form

I tried using Countdistinct and even distinct = "true" however, these seems to be working only on queryDef.

Can someone please provide suggestions on how we can implement this?

Thanks,

SSB