Very true zby. When I read the question it didn't seem to me that updating the textfield by clicking the link was desirable at all, which is why I made it dependent on the internal variable check. If it is desirable that the link is clicked once and once only then my solution is not the correct one and it would appear that yours takes that requirement in account.

Update: I've just had another look at the original question and it still appears to me that submission of the data for editing via the URL is a mistake. This in no way diminishes the fact that zby's solution solves the problem if an update via the URL is required.