Thanks for posting!
I'm sorry, it's not clear where you're running into difficulty. Could you clarify a bit? You should be able to set an input field in the Show Custom Dialog script step to point to a related record. You could even use the Go to Portal Row step to choose which row you want to insert the input into.
Hi TSBear -
Thanks for the reply; I had a corrupted button and it would not run the script. All sorted out.