Using a Groovy template can you reduce Member DTP scope in 2nd step from Member DTP in 1st step?

Summary:

I have a dimension hierarchy with multiple levels. I have a Groovy template and created a Member DTP in step one, where a parent level is selected using a formula for the Limit....@Children("Total Parent"). Step 1 works, and I can pass the DTP [Parent] to my Groovy script. For step 2, I would like to use [Parent] to reduce the scope for a separate Member DTP. For my Limit formula, I've tried every combination of formulas I can think of, @Relative([Parent]), etc. I don't receive any errors, and the prompt selection is completely unfiltered (i.e., no limits).