Callback to manipulate &to?

Based on the value of a drop-down on the form, I need to change the recipient’s email address. I can’t use the &mailselector option, as the drop-down is dynamically populated so the list of email addresses is dynamic too, and cannot be hardcoded.

Is there any way to do this? I’ve tried filling &to with a placeholder (&to=`[+to_email+]`) and using a callback to fill $fields[’to_email’], but it appears &to isn’t parsed.

Thanks!

Never mind, solved - it needed the pixelchutes work-around for PHx to be used, so ((placeholder)) rather than [+placeholder+] in my snippet parameters.