Calc to conditionally display image in container

[mackerelhead]

In a portal, I want to have an icon display only if there's a related record for that portal row. (i.e. the last row won't have an icon)

I set up a global container field with the icon in it ("iconfield"). This is in the relation that shows in the portal.

I set up a calculation field that tests for the primary key of the relation:

If ( IsEmpty ( kp_key );""; iconfield )

This is also in the relation that shows in the portal.

I know the logic is right, because this works as expected:

If (IsEmpty(kp_key);"empty";"full")

I know the icon is there, because if I simply put the iconfield in the layout, it shows up.

But using my calculation, where the icon should be, I get 0 (zero) which seems to me to say that the calculation is getting a "false" result. So I'm handling the container wrong.

Any help?

[comment]

Is the result of your calculation field set to type Container?

[mackerelhead]

You, sir or madam, are a gentleman or lady and a scholar.