The below is an extract that I've seen on another forum. It's something that seems quite interesting with regard to the last portal row (ghost row). So a calculation can be written that will either allow an object to appear on a layout or not dependant on criteria? Is this easy to do?

' I make the delete button for every portal row to be a calculation, so that, if IsEmpty ( Portal row ID ) don’t show the delete button, so the ghost row at the bottom of your portal, don’t have a visual delete button, and of course the script that delete portal row just work if the portal row ID is not empty. This method that I’ve learn make the portal looks like a spreadsheet for the user. No confuse and no user pressing that delete button of the last ghost portal row.'

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Yes this have been around a long time. To best explain this, try creating a calculation ( with text result) in the child table with a simple, Case ( ID; "delete" ). Then place this new field on the portal row.

Now if you want to use an image you can reference something like a container field that stores the image and your calc can be modified to reference that container field ( with container result )

You should see how it differs from putting an image directly on the portal.

If you're willing to use a non-graphic button, e.g. a red "X" for the delete button, you can use conditional formatting to hide it on the empty row:

In the conditional formatting dialog, use the formula IsEmpty( portal::key field ). Click "more formatting" and then set the font to a very large size like 222. The result will be the button text is pushed out of the bounds of the text box, making it invisible.

Thanks guys, I'll try and give it a go but it cannot be used in conjunction with the FM button tool can it?

Conditional formatting can be applied to the text and fill of a button but sadly not to its borders. And the fill can't be made transparent, so that's a fail if your portal uses alternating row colors.

So, for a graphic button you'd go with John's calculated container suggestion.