Not sure. What you describe is a routine use of a standard auto-enter option. If it didn't work reliably, Report an Issue would be flooded with reports of this and I'd be one of the ones posting a report as I rely on this feature in numerous places.
Are you sure that the field is defined in the portal's table?
Are you sure that the field object in the portal row is from the same table occurrence as the one specified in Portal Setup | Show Related Records From?
I got it to work. It appears to add it when I add the next portal row. I had to reselect the previous row with my script after adding the row. I guess I posted a little early. Thanks for the help.
Sounds like you just need the record to be committed in order for the look up to occur. There's a script step for that.
The advice on commit helped. It now works better than what I was doing before. I added a few steps to my script, and now it works exactly as desired. The current script steps are summarized below:
Goto Object - portal object
Set field - any field in portal ""
commit Records/Request - Skip data entry validation, no dialog
goto field - the first field for entry in the portal row.
Thanks again for the help,