Validating the field

I'm trying to validate the textarea that I'm applying FCKEditor to. Currently I need to submit the form twice before the code picks up on the fact that the field is populated - this is of course because the first submit has to fill in the hidden field.

I'm guessing I need to trigger the hidden field to be filled in when I do my own submit, but the references to this problem in earlier posts refer to setfieldvalue, which does not appear to exist in the latest release.

Little help...?