Limiting displayed values in a list based on previously entered portal rows

[Barbecue]

Hi, been a while since I posted last, and I seem to have gotten stupider, as I can't figure out what seems like a fairly easy problem.

Working in FileMaker 9 (yes, I know, but still...) I have a table of companies, a table of attribute types (say A, B, C, and D) and a link table of the attributes for each company.

I created a portal that will display the attributes for a company, and the user can add a new attribute by clicking on the first field in a new portal row, then selecting the attribute type from a popup menu.

This is all straightforward, but I'm trying to restrict the values displayed in the popup menu so that it will only show those attributes that have not already been assigned to that company.

In other words, company XYZ has no attributes, user clicks on the first field in the portal, and sees A, B, C, and D as options. He selects option C, and enters some related info. Then he goes to the next portal row, clicks the popup menu, and it displays only A, B, and D, since C is already added. Selecting A means that the next row will only allow B and C, and so on until all attributes are assigned, at which point the popup menu doesn't provide any values.

I want this to happen without the user having to leave and re-enter the record, and without using any scripting.

This seems like it should just be a matter of a few relationships and a clever value list, but I'm having trouble getting it to work. Am I daft?

[comment]

See if these can help:

http://fmforums.com/forum/showpost.php?post/274656/

http://fmforums.com/forum/showpost.php?post/233897/

[Barbecue]

Thanks Comment for providing the missing link.

I was basing a join off a calculated field using the List() function to identify which values had already been populated. I've done this in the distant past without problems, but this time I couldn't get it working.

Apparently this was due to a change in how FM9 treats number fields versus earlier versions.

Comment's example simply appended a static number to the end of the list calculation. As soon as I did the same, my own portal started working as I wanted.