[SToP_GAP]

OK, thanks for that, you saved me a lot of time wrestling with it trying to work out why it wasn't working!

For anyone else having the same issue, I found a slightly bodgy but nonetheless useful way to get this functionality (on this particular page at least). Using the earlier hook "forumadmin_start" I set the output buffering of PHP on (using ob_start() )

Then in the section where I needed to make a change, I accessed the contect of the buffer using $stringvar = ob_ get_ clean(). With a combination of this and nested output buffers I was able to do exactly what I needed.

This required a plugin for both the "forumadmin_start" hook (which turns on the buffer) and then a separate plugin at the hook point where I'm dealing with the buffered output, in this case "forumadmin_edit_form".

This is not perhaps advisable for mainstream pages as it'll introduce additional overheads on a system, but for backend pages it shouldn't cause any issues. There is potential to clash with other plugins which manipulate the page at the same time as this, especially if they do anything with the buffer so tread carefully.