Updating custom field values *before* messages are sent to the watchers

I followed
http://wiki.bestpractical.com/index.cgi?EditCustomFieldsOnUpdate on
how to add the custom fields to the update page. One problem I
encountered is that the custom fields are updated after the mail
messages have been sent to the watchers. I’d like to get the updated
custom field values in the Resolved template. Any idea how to solve
this problem?