There already is such an option! You can add a content filter rule with an action to Add/Edit a Header such as:
X-Bayes-Score: ####BAYESIANSCORE####
You can see a complete list of available field tags by clicking
http://www.code-crafters.com/abilitymai ... dtags.html. This list is also available in the AMS help manual under Tutorials -> Using Field Tags. To open the AMS help manual, press F1 while using the dialog admin interface or access via the start menu.